I
loathe mercenaries. But they should have been in there too. The Ferengi would definitely use them, and the Allies would be desperate enough. Nausicaans,
Chalnoth,
Corvallens, etc - they'd all be for the hire, I think.
More than that, they could have just thrown in a bunch of ship models they already had into the battle scenes for these smaller powers that would have very likely taken sides even if they didn't get much screen time in the board-meeting scenes.
Ships on both sides, that is. Maybe the Sheliak,
Yiridians,
Dopterians, or Miradorn would have signed on with the Dominion.
Other cultures also were missing. The Cardassians used the
Xepolite and
Kressari to run supplies for them...maybe something about the Allies targeting such Cardassian supply lines.