if you make a second class of missile, you can take off one point of warhead (8 seems pretty solid against fighters anyhow) and probably some fuel.

i personally haven't run into trouble with having minimal range on-board sensors.  i feel like a human opponent would abuse it, but probably i have a dozen fatal flaws that would show up in pvp.

being able to refit sensors and fire controls is probably my favorite perk (other than less clicking) of building big ships.  with new missiles and new fire controls a missile boat goes a GOOD LONG TIME before accumulating crew grade ceases to make up for tech obsolescence.

well aint much to change after that, maybe engines if you really want to. you could probably keep them running for 50+ years with the right refits.

If you have 3 scout fighters - one res5, one res20, one res100 - it's not too much micro to put them in a Scout Wing under their Mothership in the Naval ORG tab and then launch/retrieve them with a single button. If you can learn how to use the escort commands to make them always fly X amount of km ahead of the main fleet and then save that order, you've reduced the micro even further. That can give you very good early warning of what sort of threats are coming your way in a very cheap manner. A human could mislead you on purpose but the VB6 AI will not.

if it were me, i'd pick a class i intended to have ~8 of per fleet, just find the space for a size 8-12 active, and have 3-5 variant classes (the res 40 is good but optional, a thermal is good but optional).

And THAT is the idea I really needed to solve this.  I can make 3 variants of the Ajax class, each with a one size 8-12 sensor of varying resolutions.  The Patroclus already has a res 1 sensor, I can beef that up slightly which would also allow me to push out AMM intercepts a bit.

Missile sensors is probably the proper solution to the overkill issue, as that will also reduce the number of missiles I waste in fleet engagements.  How much range is required for re-targeting?  Or more precisely - is re-targeting instant or is there a 5s lag?  All targets would presumably be in the same task group/same location, so if it is instant I assume 10K range is enough otherwise I guess I'd need  5*target speed range (30-60K).  With current tech I can get 60K range at res 5 for .323 MSP.  I may also want to increase my missiles to size 5, as the missile calculator shows a big reduction in hit chance if I include 60K active sensors. 

If the enemy uses missiles that are similar in range to my own I don't think I have a realistic shot of detecting/engaging missile fighters unless I create a dedicated sensor/flagship.  I'm at Grav 21, EM 14 sensor tech.  My current AMM res1 radar will spot anything bigger than a missile at 14.7M, equivalent to a 2.25 size res 5 sensor.  Swapping my size 6 res 100 sensor for size 8 res 40 reduces range to a still-adequate 148M but will only detect 250 tons at 2.3M.  Going for size 10 res 20 gives 131M range, with 250 tons detected at 8M. 

Assuming tech parity - fighters that are 50% 2x overcloked MP engines should have a speed of about 12-13K.  If I'm facing beam fighters that are closing at that rate I'll get one full 400s ASM salvo off for every 5M detection range, or one salvo per 3M if I try to hold the range open after detection.  So if I can spot them 30M out I can empty the magazines before they get in range.  At my current tech this would require a 4.5 size res 5 sensor.  And in this scenario I would need multiple fire controls on the Ajax as dividing my fire by delaying it would allow the fighters to maximize their point defense.  Whereas not dividing my fire would result in massively expensive overkill.

Based on my chosen ship size/speed/range I have 155-165 HS of payload (sensor, eccm, fire control magazine, launches) and 218-228 HS of overhead.  I'm not sure allocating this much tonnage to sensors is a good idea, and researching large sensors is really expensive.  So I may create shell versions of the missile ships (no fire control or sensor) and push research of Grav sensor 28 then refit the sensors in after the base ships are built.  This should cut sensor size down to 75% of what I need with current tech which is as good as I can get any time soon.  And that way I won't have to wait before starting construction, nor will I have to double-buy the sensors.

Given my ASM range of 126M is ship detection at 150M and fighter detection at 30M reasonable?

I guess that's the primary issue then.  I don't have any opponents yet, so I don't know what I will be facing.  And as I have no combat experience I don't have any real intuition about what I should be worried about.  As an example - the Achilles fire control decision assumes that 16x 85% gauss shots would not be overkill for swatting fighters, as I would expect any fighter which closes to that range to have at least 2 layers of armor.  I went with Res 100 sensors assuming that ships which were less than a quarter of the size of my own would not be a major threat - which I know now is invalid. 

And of course I have the impossible to fulfill expectation of being able to build a fleet that can handle everything without bankrupting my empire and which doesn't simply handle everything equally badly.

So I guess what I'm realistically shooting for is a general purpose fleet without any glaring weaknesses as a core.  I'll send a few stealthy fighter scouts in to try to get a feel for what I'm facing, then build supplemental specialty ships or fighters to address whatever I can glean from the scouting report, or from how the scout was destroyed.

My expansion timetable is currently on indefinite hold.  I explored the 16 systems within 2 jumps of Sol in the first 15 years, then encountered a wreck and and a ruin on the first system 3 jumps out.  At that point I put a hold on expansion while I developed what I had discovered and researched warship techs.  Over the next 20 years I have terraformed 13 worlds with 3 more in progress and another dozen in the queue, half cost two the others below 5.  Across the empire I have about 1,800 construction factories, 1,400 automines, 70 research labs, and 1.5 Billion population.  I'm setting up mineral relays back to Earth but I'm still working on mining infrastructure - at the moment they are only returning with holds 10% full.  I have large high-accessibility deposits of every mineral but corbomite - mostly I just need time to build more mines. So the only spur for expansion is my own impatience as I still have a lot of development to do on the systems I've already explored. 

My doctrine had been to build a jump gate then survey the system while the gate builder creates a return gate.  I'm going to revise that to sending in a few scout fighters first to check for unfriendlies. The fleet will be summoned to clear and hold the system while gates are built. 

Going with size 2 HTK/17 cap size 1 magazines will net me a small storage gain at the cost of making it harder to store an exact multiple of the volley size.  I designed magazines which held multiples of 60 to make that easier.  My current magazines 60cap/4HS, 180cap/11HS, and 300cap/18HS

Lack of res 10 sensors/fire control is a significant flaw, thanks for pointing that out.  Would 55M range be sufficient for detection (6HS, res 10) or should I push that all the way out to 120M (13HS)?  Or should I be looking at res 5?  6HS at res 5 gets me 39M range.  For the Achilles - it mounts three fire controls already so I'm not sure why it would need more.  The railgun is there to help punch out unarmored fighters but mostly it would rely on the lasers.  Not that it would be very good at the task as it is primarily anti-missile - the gauss cannons would probably have to sandblast for awhile to be effective. 

My ASM are 9 damage, so I don't think they will be overkill for fighters, but one hit may mission kill a fighter.  I don't think it is feasible to design a 4 damage size 1 missile at my current tech.  I should certainly put a res 10 fire control on the Ajax, and two on the Patroclus will only be .2HS each for 5M range so that's an easy add.  I don't see the need for more than one on the Ajax though - 400s reload time on the launchers means I could fire each tube individually and still have to wait for them to reload.   Am I missing something?

big picture, the fleet design looks ok.  two medium sized things i'd like to critique

from direct experience "ill just leave my fleet in a closet for a third of a year while i build a gate" at best will seriously mess with your expansion timetable, at worst is an existential threat waiting to happen. 

your fleet has a pretty serious vulnerability to fighters.  your sensors are res 1 and res 100, which makes you bad at spotting and engaging them, and both your anti missile designs have high ratios of weapon to fire control, making you bad at defending them, especially achilles whose 8 turrets are worth almost exactly the same as 2 turrets in this situation.

i would recommend, in addition to just getting more fc on the defensive units, producing a variant of ajax with a res4 or res5 active, and making sure all ajax have a second mfc in the smaller resolution.  your asm is pretty close to what i'd design as a specific anti-craft missile , and missile based fighter wings are pretty much inevitably glass cannon.

I prefer 1 HS magazines, to increase the HtK of the magazines.  Also, I greatly prefer to rely on scouting than stationing a large fleet forward.  I like the explanation of why you have a 6 month minimum deployment.  Something that doesn't show on the tooltip is that Factory bonus naval officers increase the construction speed.  But I wouldn't start building a jump gate without having thoroughly scouted the system first anyway.  Different styles, I guess.

It is certainly a doctrine that is consistent with an interesting RP, and makes for an interesting playstyle.