One of the great unanswered curiosities is, what would
Phase II have really been like? In context of its time, and in context of being a follow-up to TOS at a time when the movies hadn't happened and there was very little Star Trek to compare it with?
I mean, despite TMP obviously evolving from it, we still have very little inkling of what it may have looked like, or how much closer to TOS in feel it might have been. The test footage that was shot shows actors wearing variations on the TOS uniforms, and the sets, despite in some cases being the same ones seen in TMP, have got a much more artificial look - the doors of the engine room are painted in a basic primary color not unlike the house style seen in TOS, not the sleek sheen that Bob Wise ordered be applied to the sets when he took over the production.
While the format documents hint
at Phase II being more of a ensemble than TOS, to be honest the format documents for TOS were almost the same.
My bet is that had it gone into production, it's possible Phase II would have literally been a slightly updated TOS - not yet confident enough to go all out and do something different like in TNG, it might have been mired even more in basically being seen as a belated TOS season four.
We'll never truly know, but it can be fun to hypothesize