I haven't read it yet, but doesn't the Marvel comic Star Trek: Untold Voyages make the case that the original Marvel run was part of a "new ongoing mission" between TMP and TWOK? I was told that aside from some wonkiness about setting up TWOK elements a few years earlier than it should, it seems to work fairly well as "bridging" the Second Five-Year Mission concept.
^Uhh, the original 1980 Marvel run was explicitly presented as a new ongoing mission after TMP. There was no need to retcon that later; it was overtly the case from the beginning. Just about every post-TMP novel or comic since then has been, has had
to be, in a post-TMP ongoing mission, so it was hardly an innovation for Untold Voyages
to follow that established precedent. And UV didn't reference the 1980 run in any way, as far as I recall. The '80 run wasn't that well-regarded, and I doubt Marvel was eager to remind people of it.
Actually, the first issue of Untold Voyages does
feature some subtle references the early '80s Marvel run with the character-design of the Klingons aboard the K't'inga
-class battlecruisers -- they're pretty much a spot-on recreation of their TMP "lobster" appearances (in the sense of looking very much like Cockrum's interpretation), as well as in smaller details like how the Klingon captain fires his disruptor, the disruptor's appearance, etc.
Not HUGE, obvious references, of course, but I remember being pretty thrilled to see all the love given to those Marvel-motifs in the '90s when Untold Voyages
first came out.