From a pure ops perspective, I strongly doubt that the sprungs or parade soundstages could be used during daytime ops due to backstage movements. Parade floats moving around and character integrity backstage alone would probably stop that.
So then, that leaves the soundstages, Shrek, and MiB.
Shrek really could be done, but it would be difficult to make queue space for it now that Shrek is actually using its queue during the day. Plus, I doubt that Billie's publicity team would want her image associated with any event encouraging gathering in a pandemic, especially one being kind of thrown together. So that rules it out.
Then you have MiB and the Soundstages, all of which could realistically be run during the day, but between distancing and likely necessary pulsing, would require pretty long queues that only some could probably accommodate. So, Virtual Line might not be a bad idea, except I don't *think* they could do a Virtual Line unique to an upcharge ticket. Universal's VL system is entirely location based, so you don't even have to be in the park to get a pass (just in the area). So realistically it is probably an either/or situation.
As for which houses could be opened for daytime ops, I could definitely see Bedtime Stories getting pushed out (A&D is probably tired of waiting on that one, haha) and even Icons (it would satiate the need for nostalgia). TCM is a house that I could honestly see just getting lost to time (I don't think they'd want to "activate" the IP, and I don't think they'd want to hold onto it either). Brides however, I think is neutral enough to where it could probably hold up. Finally there's the Anniversary house/ Carey House in MiB which... seems like a toss up. On one hand they have FFL right there for extra queueing space, but otoh I could see them wanting to keep the houses consolidated to one area.