If I have one major gripe about the show, it's the way it was constantly padded out with filler eps at a time when JMS's ability to get the core storylines finished was still in doubt. The threat to S5 and resulting hasty rearrangement of S4 meant that the final season didn't hit with the weight it could have done; it felt like an afterthought rather than a climax.
Reflecting on that experience, I think the major flaw of B5 is that, in structure and intent, it was twenty or more years ahead of its time. Given the handicaps under which the creators then had to labor, it's even more remarkable how much they accomplished - B5 might have been the very first example of what we today call the 'binge-worthy show', made on a shoestring in a time when syndication and time slots and missed episodes were still problems that a show could have. This show overcame them admirably - even so, I can't help but wish a little for the chance to see what the same people could've accomplished today, with the kind of resources available for something like Stranger Things.
That won't happen, of course, not least because the show is niche even by comparison with something like Firefly. For the same reason, even a Trek-style HD remaster is unlikely - a shame in its own right, since the then-revolutionary CGI space effects are by far the part of the show that's aged most badly, and a shame all over again because the creators were looking far enough ahead to shoot in 16:9 and 5.1 surround throughout, which would give an HD remaster the kind of payoff that, if we're being honest, the ones done for old Trek shows never really have.
In any case, it's a small miracle the show got made at all, and another that it ended up being so close to what JMS intended it to be. Anyone who can enjoy TNG or DS9 today can, I think, enjoy B5 at least as well, and on that basis I recommend it without the slightest reservation.
Sadly, such an approach is impossible for the majority parts of the latter series (DS9, VOY) since their effects were mostly CGI, and rendered directly to standard definition video. Further more, many of the 3D models and scenes have been lost, so it would probably require a total effects re-do from scratch (on top of film stock scans), which is "a very costly proposition with questionable (financial) returns".
The thing about B5 is that few of its space scenes involve much compositing, since they were all CGI from the start and compositing was hard back then. For that reason, I think a space-effects redo would be unusually feasible for that show, albeit still too expensive for anyone to actually do one.
A harder, if smaller, remastering issue would be that they shot practical effects on video and special effects on film, largely due to that being the cheapest option for both. In standard definition you can't really see the difference, but watching the show today you definitely do.