I have a suspicion that warship sizes will peak at a certain point and not go beyond it.
As I see it, the practical limit for a ship's size is how many years it takes to build, and therefore how long it takes to be overhauled. I can see ships that take as long as 5 years to build. Sure, it would take a year to overhaul them, but that is 3 years of use per one in the shop.
But a ship that takes 15 years to build? That would be in overhaul half the time. I could see technology developing to the point that new technologies are so expense that a significant improvement in technology wouldn't happen for decades at a time, so it wouldn't necessarily become obsolete while it was being built.
When technology is changing rapidly there is a premium on ships that take less time to build. Even so.
If five years is the practical limit, five years is the practical limit regardless of the tech level, unless larger ships are so much more effective on a cost basis that it is really worth the hit.
So if at the 2050 tech level the largest practical warship is around 300 HS, what developments would increase or decrease that size?
At Tech advances, every system becomes cost denser. They cost more per HS. Instead of an average of 6 BP per HS, it edges up to 8 HS, 10 HS, and more. That means that by advancing a tech generation, a ship built along the same general lines and HS might cost 10%, 20% more.
Factoring against that there is Increasing Shipyard Construction Rate and finding an officer with +30% shipyard build rate. And I think that cost goes up faster.
Among the implications:
Since number of shipyards can be expanded far more easily than shipyard construction rate can be increased, it will be easier to build and maintain a large number of warships than it will be to make superhuge warships.
Still, if we put an upper limit of 15 years construction as an estimate of what sized ship will be built, that still means ships of 1,000 HS - 2,000 HS are possible.
But I am neglecting some possibilities. There might be weapon systems which do not radically increase in cost density as tech increases. Hangars won't increase in cost per HS, after all, and fighters come under different maintenance issues. An expensive fighter load would not make a carrier take longer to overhaul.
Hunh. I just noticed that armor caps at 20. I went up to crystaline armor, and getting up to level 20 didn't even double the size of the ship.