"Did you watch a version with Barbara Bain edited out?"
No, but I wish I had. Bain and Landau had all the chemistry of a hard vacuum.
Barbara Bain's acting was unforgivably wooden; in most episodes, she's part of the scenery, not the plot.
The 2nd season's minor "reboot" by the much-maligned Fred Freiburger introduced a new set of younger, more photogenic, leads who acted rings around Bain and were less likely to phone in their performances.
To be fair to Freiburger, he was more unlucky than terrible; there were some good episodes in _both_ seasons. Unfortunately, there were a lot of duds in both too, and the pacing in the first season was often glacial. Space:1999 looked great, but that's about all it had going for it.
Incidentally, it wasn't unusual to show series episodes out of production order back in the '60s and '70s, so each episode was usually treated as a standalone, sharing only the basic premise and the main cast. Series continuity wasn't considered important and writers didn't often bother with it. Recollections of strange character progressions are likely to be a result of this.
UFO was a _much_better series, with a more plausible premise, but I think Blake's 7 is more deserving of a revisiting by modern production standards: a very simple premise with some very strong parallels in today's world.