touches upon a race like the Preservers from TOS
This one I have never understood. The Preservers maintained status quo by abducting a small cultural subgroup of an existing species a few hundred years ago. "The Chase" dealt with folks who changed everything by introducing millions of all-new species in a grand scheme spanning aeons, four billion years ago!
IMHO, seeing the Preservers as tying into "The Chase" is akin to seeing "The Savage Curtain" as dealing with the extinction of whales...
Well the facts are this direct mention was considered by Moore. It was my first thought when seeing the episode. I have no problem believing in a multi tier plan to seed or protect races, similar plots exist in 2001 and Contact, and also have no problem believing a civilization could exist for a 5 or 6 billion years in a stretch. The idea they may "pass on" not only exists in literature but also Star Trek itself.