I was reading both the Minbari and Centauri factbooks. They both point out that there is a faster then light propulson system.
The two books are just plain wrong on this point
No race in the B5 universe uses real space FTL drive (jms confirmed this at somepoint I seem to recall...).
No one needs to develop it due to the presence of the jumpgate network and the relative ease with which said equipment can be reverse engineered.
That said, realspace FTL, along the style of Star Trek's warp drive, is actually plausible - just not practical (yet... and not for a log while until material science improves considerably).
Once you're effectively through the light speed barrier, there's no constraint beyond how much energy you can funnel through your warp drive to limit your FTL velocity, so there's nothing to say it would be inferior to hyperspace travel.
In the Babylon universe, any race with gravitic drive is actually a large chunk of the way there, as basically these are low power warp drives however the impetous to develop them towards FTL drives just isn't there.
Maybe, given millenia of research that could happen, but why waste the effort and resources when you can develop your sensor technology to make hyperspace travel safer at higher velocities.