If the Narn are really lucky they can dump E-Mines so they hit both fighters and carriers. With that many fighters some might have no choice but to be mixed in. Heck, Narn players might be willing to drop E-Mines in nasty furballs consisting of a mix of Narn capital ships, Gaim cap ships, and fighter swarms. Even if they haven't become suicide bombs and pass the Fleet Carrier survival roll, this gives the Narn another turn to pound the carriers in hopes of killing a few(and whatever regenerated fighters are in them) and thus gutting some of the Gaim thrust.
Of course this is all theory as I don't have my 2nd Edition stuff yet.
The Pak'Ma'Ra and Brakiri also have area effect attacks right? So they should be able to operate similarly to the Narn as a reaction to the Gaim. The EA while not having the fighter swarm of the Gaim have lots of fighters still so combined with their ships presumably being more combat capable should also have a good shot. The ISA, Drakh, and Minbari strike me as possibly the most vulnerable races since it sounds like the Gaim strengths specifically exploit their weaknesses.