well, one thing to remember about mods that use research-linked caps-
they probably do this to create a sense of progression, and in the case of some mods (Dawn of Victory comes to mind), to create a sense of scale. I think that for vanilla Sins, capship research wouldn't really be very interesting.
Well... This sounds like the exact reasoning for research linked frigates and cruisers. It's interesting this exists for basic ships but not capital ships.
Here's my reasons- all three races, by the time the Entrenchment period came around, were able to build all types of capital ships (in the very beginning, the Vasari&Advent are really the only ones able to build their entire fleet roster, lore-wise). Thus, research for caps wouldn't make sense lore-wise, would probably be opposed by the MP community on the basis of- wanting all the caps out at the beginning (not literally, just the potential), and wanting games to be shorter.
Ya, the MP community would fight this because early game is about rushing to take out the suicide or aggressor positions. No issues there. It's just an interesting argument because everyone wants cap ships that are better and last longer which works for the current carrier cap, but if you build a late game capital ship it still starts at the low level and get dissentegrated fairly quickly in battles. So most people build masses of LRF's with either carriers or flak.
Also, the lore argument makes zero sense to me. You start out every game the exact same way, zero military labs and zero civic labs and access to scouts, LF and colonizer. You have to research everything except for the most advanced military units in the game which somehow get obliterated by LRF fire. Personally I would rather have access to kick butt battleship mid game than the pathetic ones available currently. Until this changes I'm pretty much stuck with colonizer/carrier or dual carrier.
Don't get me wrong I like this game and the MP aspect is extremely fun for competive play, it just doesn't expand beyond 3 military labs and 3-4 civic labs depending on race with minimal research inbetween for most 3v3, 4v4 or 5v5 games. The multi-star games like Doppelgangers is really where you see diverse fleets and eco come out in MP.
As I said in the OP, this probably wouldn't happen for the game, if I do it for a personal mod so be it.