I don't know if we're just talking about designs or wholesale new races...
First and foremost, Late Earth needs skirmish ships. Not one, closer to three. Preferably, not boresighted.
The Drazi need a Scout. The AoG Eyehawk may be what the doctor requires.
The Vree need a Hull 5 Skirmish ship, even if its firepower is poor. Perhaps an uparmoured Xurr with its antimatter converters? They also need a dedicated carrier, the Xeel. The Tzymm needs a place from which it can excel.
The Abbai could really use a Jucaya so they can be fielded legitimately in a campaign as a race unto themselves.
The Raiders need .... a lot of work. Sigh. They need a lot of ships, too. 2 pure raider hulls with move of over 8", one a Skirmish and one at Raid, would make a ton of difference to this fleet.
The Narn need the T'Rakk. Just because it's so flippin' obvious.
The Vorlons need something antifighter (although something to this effect is hinted at in Armageddon), and the old Destroyer Escort from AoG days should do nicely. There's also evidence of Vorlon Light and Heavy Carriers, which should be considered.
The Minbari need another Skirmish hull that can survive the Stealth changes. The tactical ideas behind the Torotha don't quite match what Armageddon currently demands of them. I can't find a good AoG hull to fit the premise now, though.
The original B5 stuff included a Shadow Destroyer that was based on the Scout hull. Shrug. A Raid hull without the stealth? Maybe Armageddon's already handled this.
The Dilgar, at least, and probably the Drakh need bases for campaigns.
The Dilgar could also use a bad light carrier, Something slow, Raid with almost no guns. A Dilgar Balavarin. Not a good ship, but it'll do in a pinch. A Rohric carrier variant, then? Rbax's Ochliavita-B may be another alternative.
I doubt that the Drakh work against the new fighter rules. The damage might be ignorable, but the crits'll just pile up. Without fighters of their own, it gets really dicey really fast. As fighters move after raiders, there's almost no reason for a fighter to ever end up in the anti-fighter range systems on the Light raiders. Something doesn't work here. A specialist escort raider would do the job -- T arc, Anti-Fighter ... and can't hurt a Capital ship for beans might be the call (Range 6, Weak, Anti-fighter, maybe 6 dice or so?) Or, just make a Drakh fighter. Access to Sentris and/or Raziks might be perfect, if a cop-out.
In terms of something new, I'd suggest the Gaim. Bulkhead rules should be interesting. I could see special rules about how multiple ships combine to form one Particle Concentrator volley. Should be unique, but will be a bear to balance.