Your fighter is barely faster than capital ships of the same tech level, the 21 billion km range is excessive, it has far more MSP than it could ever conceivably need, and the loadout of 2 size 2 missiles (or 1 size 4) is laughable. 18 million km's is also a bit excessive range for a mere size 2 missile, imo (I prefer 8-12 million km at lower tech levels).
I am not looking for a fast fighter - think of more of a PBY flying boat that can be built in the years it takes to get to higher tech levels and then train the new fighters up to snuff.
The range was so that I didn't even need to build or use a carrier to ship them to a system, they could hop from one colony to the next.
I do agree that the 2x2 box launchers was anemic - its why I updated to the 1x4 setup.
I like range on my missiles - many ships would never detect the fighters as they launch and have strikes on the ship.
If you want a cheap patrol unit that can travel between systems, I'd suggest using FACs instead. You'll have more hull space to work with. Because fighters are so small, it is important to cut as much fat as possible. This allows them to carry as much punch as possible while also being as fast as possible. I understand the reasoning behind your design notes, and that these fighters are intended to provide a cheap and low-maintenance military presence for outlying colonies. Unfortunately the result is a design that is too slow, too long-legged, and unable to meaningfully contribute to a fight once it gets to its destination.
a squadron of these craft (10 missile carriers and 2 sensor craft) would be equal to 6 FACs (Five missile and 1 sensor) - while not using up limited shipyard space.
At the same time, they have 90 year lifespans. Once you have a backwater colony with x million they will demand defense. Drop off 1-2 squadrons of these old fighters and you will keep the population happy without maintenance yards or other logistical issues such as maintaining a wide range of materials to maintain the FACs.
For carrier operations, I find that an operating range of 4-10 days is sufficient, while engineering spaces are not usually necessary for fighters at all.
These are not designed for carrier operations in mind.
And honestly, the most practical solution to provide that initial presence for colony systems is just to build a small troopship and drop off a garrison battalion there to control unrest. Meanwhile you simply wait for your tech to mature a couple levels before investing in your first actual warships. If anyone is assaulting your systems while you are still at tech level 1 or 2, you probably won't be able to stop them anyway.
I am not expecting my "Backwater patrol craft" that I build for dirt cheap in the early game to stop a invasion. I just want slots for my Lt. Commanders to command early game, and a simple way to keep a system content. Unlike FACs they don't cost to maintain, When playing a conventional start it might be 10 years before you can make decent ships and FACs, till then you can make 3-4 squads of these for a song. Also if you have someone in system in the start, it can be useful as well.
I am well aware that these are not high tech carrier fighters -- but they were not designed as such.
