We already have the ability to use missile launchers to shoot any type of missile as long as it fits. The ability to just swap-on-the-fly missile launchers with lasers or of violating launcher sizes as long as some arbitrary "total" isn't surpassed, goes against my sense of realism and immersion, nor does it seem like something that is really needed.
Mostly agreed. I think the modularity concept can get you as far as box launchers, by their nature a self contained empty space meant only to speak to an adapter which relays to a munition, where the munition is all stages of attack by itself, requiring the launcher only to turn on, get told who to attack, and when to begin. We have modern examples of quadpacking VLS launchers from numerous nations now, across multiple weapons systems, requiring no physical alteration of a design that predated the new munition.
The modularity exists within the canister, you engineer your munition to play nice inside a canister, and the vls system doesn't care very much after that.
It is realistic to accept that a large enough box launcher could receive an insert for two or more smaller munitions per box launcher, the US navy has been doing operationally it for almost 15 years.
As for anything not a box launcher, its a complete logistical train, involving generation/storage of ammunition, transfer of ammunition to the launch point, a re-loadable mechanism to fire more than once, and a complete wiring interface to communicate what stage of this process it is at when queried.
Gun pods on external pylons? Not without torsional stress tests for the mount, modification of wiring to support the needed functions of the new weapon pod such as ammunition remaining. And those wiring changes will need to be extended from the pylon/mount point to the central computer system, and from there to the cockpit for the pilot can be aware of what it is doing/control it.
Missiles? The F-14 could haul around the much larger AIM-54(460kg), yet never could fire the AIM-120(160kg). Instead it had the AIM-7 sparrow, also heavier than the AIM-120 at 225kg. It wasn't wired in a way compatible with the AIM-120, the on board computer didn't know what it was, and the firecontrol couldn't talk to it.
The F/A-18 Growlers are literally just F/A-18F's with a few extra microwave generators and receivers bolted on. A carrier at sea cannot perform the task of uprating another F to the G model. they can overhaul the engines, perform complete engine swaps. Can't uprate the model from F to G, there's too much involved for it to be a field task, much less a hot swap, it is a workshop task, a refit.
Just because ah-64's can have 4 4x racks(16) of hellfires doesn't mean you can go hang a rack on each of the 11 pylons under an A-10 to go play tag with tanks in a couple of hours-not wired for the missile at all, nor can you load 11 mavericks, despite the A-10's being wired for it--on some pylons.
In Aurora, we already get greater freedom than this, the software/firecontrol updates being abstracted away when you load the newest in a series of missiles. Just have a missile fire control, have a suitable launcher, and the weapon in the magazines, and the weapon will work.
For warships larger than fighters perhaps then?
No naval vessel has ever seen its gun armament altered as easily as reloading ammunition. There are logistical and structural issues with the weapon to account for. The closest naval ships get to this capability are the littoral combat ships. Even they are not quite hot swap. Its a days in port sort of task. They've done it in 96 hours before during rimpac in 2012. Effectively a non-destructive, reversible refit.
No naval vessel with rail launchers has ever hotswapped its missile armament to missiles it wasn't designed for initially. The Oliver hazard perry frigates lost their missile armaments as a cost cutting measure, in large part because they were limited to the outdated SM-1 missiles. By the time they were stripped of their missile armament, the US was testing anti ballistic missile missiles like SM-6. Their magazines may have been able to hold the larger missiles, but the reload mechanism, and the rail launcher couldn't, and uprating the launcher to be the same as that on the Tico's was deemed too much effort, because it would be quite a sizeable overhaul.
MK-41 VLS could UNREP at sea at a rate of 3 canisters per hour.
https://www. dtic. mil/dtic/tr/fulltext/u2/1032180. pdf . Lifting one out is considerably easier - no need to perfect alignment before lifting, just be close enough. Call it 30 minutes to perform a cell unload/load operation. 90 cells, in two banks(29 and 61) that can both be in progress simultaneously, you can rearm the ship in 31 hours.
In replacing a canister, you also replace the insert contained within the canister, which means you can hot swap from single weapon of one size, to quad packed weapons that are smaller. 2+ cells of complete mission/armament change/reload per hour at sea seems to fit the bill, if slow.
Its not a weight or attachment issue, its an everything else issue.