Shadow Omega

Earthforce Omega carriers rebuilt with Shadow protection and beam weaponry but standard engines and fighters. The higher mass rating of the Shadow Omega is because Shadow technology is much more compact, not because the ships are any bigger than before.

The Shadow Omegas only fought for Earth in the TV show, but not with other EarthForce ships. I think it reasonable to assume that they would have aided the Shadows if needed, since being loaded with Shadow technology it would have been impossible for them to disobey, and they add some variety to the fleet.

The Shadow Omega is well protected, by B5 standards anyway, and more heavily armed, but still has the original hull structure which is weaker than the mass would suggest.