[Suicide Junkie]

It dosen't have to be ages, it could be racial techs (or even both). Just disallow the "ages" tech tree, and enable "B5","ST","SW", etc tech trees during game setup.
Please don't homogenize all of the SF universes.

In regards to B5 ships, their weapons are decently powerful, probably within an order of magnitude of Trek. Putting ten B5 capital ship beams into a Galaxy class ship should breach the shields pretty quick, and they could win (with heavy casualties, though)
I'd image the fight to be like a BattleMoon vs 20 DNs, or a bunch of frigates against a baseship.
A completely valid way to fight a war.

In terms of population & morale, B5 races are used to grinding, high-casualty warfare. Trek races would be more sensitive to losses, but have fewer, larger ships, and thus fewer losses to get upset about. Giving a reduced unhappiness from ship losses to B5 races would be a good idea.