One of the issues I have with Unification III as an idea is while the final re-unification of the Vulcans and Romulans means a great deal to us, it won't mean shit to the Discovery crew.
I mean, I suppose the Earth-Romulan War did happen shortly after Enterprise. But no human saw a Romulan and lived to tell the tale. In order to have the story make sense, the uptimers are going to have to explain a lot of shit to the Discovery crew that Trekkies know already.
I think that, part of the reason Burnham arrived where she did (3188), compared to when Discovery arrived, is to do a lot of that info-gathering off screen. If Burnham has had access to any type of Starfleet database, which we must assume she has given where she was when we saw her last, then she could very well have read all about Spock’s exploits with the Romulan’s, etc. Hell, Spock’s great regret was being unable to save the Romulan’s (nor to unite them with Vulcans, prior), so if Burnham has access to any of that information, I feel like she’d have a sense of duty to help complete what was pretty much Spock’s entire work for the second half of his life.
Honestly, I’m just hoping we get to see Burnham react to the fact that Spock disappeared, and was never found.
1) Spock had no descendants
Well, we don’t know that, do we? We didn’t see the second half of his life, and we only really got a glimpse at the first half, even. Given he kept the existence of Michael and Sybok quiet, it seems logical he’d do similar about children?
If not, his “descendants” don’t need to be blood, in this scenario. Anyone following his teachings, would work. And, if anyone was going to leave something to be given to Michael in the future, you’ve got to assume it was Spock.