It seems worth noting that there is still a "improve institutions" vs "improve capabilities" race going on in frame 3. (Though if you think institutions are exogenously getting better/worse over time this effect could dominate. And perhaps you think that framing things as a race/conflict is generally not very useful which I'm sympathetic to, but this isn't really a difference in objective.)
Many people agree that very good epistemics combined with good institutions would likely suffice to mostly handle risks from powerful AI. However, sufficiently good technical solutions to some key problems could also mitigate some of the problems. Thus, either sufficiently good institutions/epistemics or good technical solutions could solve many problems and improvements in both seem to help on the margin. But, there remains a question about what type of work is more leveraged for a given person on the margin.
Insofar as your trying to make an object level argument about what people should work on, you should consider separating that out into a post claiming "people should do XYZ, this is more leveraged than ABC on current margins under these values".
I think the probability of "prior to total human obsolescence, AIs will be seriously misaligned, broadly strategic about achieving long run goals in ways that lead to scheming, and present a basically unified front (at least in the context of AIs within a single AI lab)" is "only" about 10-20% likely, but this is plausibly the cause of about half of misalignment related risk prior to human obsolescence.
Rogue AIs are quite likely to at least attempt to ally with humans and opposing human groups will indeed try to make some usage of AI. So the situation might look like "rogue AIs+humans" vs AIs+humans. But, I think there are good reasons to think that the non-rogue AIs will still be misaligned and might be ambivalent about which side they prefer.
I do think there are pretty good reasons to expect human vs AIs, though not super strong reasons.
While there aren't super strong reasons to expect humans vs AIs, I think conservative assumptions here can be workable and this is at least pretty plausible (see probability above). I expect many conservative interventions to generalize well to more optimistic cases.