@UKcommander:
Also, what do you think about giving the Romulans two capitals, Romulus and Remus? I know they are extremely close to each other, but still, they are the Romulans capital planets. However, that would probably mean that I would have to give the UFP four capitals (Earth, Vulcan, Andoria, and Alpha Centauri) and the Dominion two (Founder Homeworld and the Vorta homeworld). What do you think? Thanks for your interest and the compliments. Sorry for any spelling mistakes.
Only give the Romulans two capitals because for the Romulans both planets are significant. For the Federation during the Dominion War, Starfleet was only worried about a Dominion assault on Earth, not on Vulcan or any of those other worlds.
I would suggest allowing the Federation, Klingons and Dominion to research improved ships. Give the Federation Galaxy, Excelsior, Nebula, Ambassador etc. classes first, with Steamrunners, Akiras and Sovereigns etc. researchable.
Also, make a timelimit for when the Dominion controls Deep Space Nine, say, 12 turns. If the Federation does not liberate DS9 within those 12 turns, then for every round after that, the Dominion get a few ships as reinforcements for successfully destroying the minefield. You should also have starbases as repair areas and maybe you can incorporate torpedoes as weaponry that can be carried and fired by starships.