Only done some quick tests and the odd opera practice recording so far, but I think it should be doable. You’d want a transparent and neutral sounding mic setup for this, though, as an up-close dynamic stage mic might not be the easiest thing to fit into an orchestral/choral style mix. I suspect that with choir or opera singing, there might also be more to the proximity effect than just frequency response, in a similar way to violin, cello etc, where the instruments start to sound like electric ones if the mic mainly picks up sound from the area directly under the bridge.
Either way, dry vocals will have the same problem as dry instruments when it comes to positioning them in the mix. I suspect spatial mixing tools can come in very handy here as well. Nothing that can’t be done manually, but if you have umpteen separate mono sources, it’s real handy if you can just move a marker around and have all the parameters calculated.
As for the “choir” part, I suspect it’s important to get a good blend of timbres, so for a “solo choir,” it’s probably a good thing to be able vary the tone a bit between parts. Formant shifting might also help (works great for pop, EDM and the like!), but I’m no sure how much of that you can do before the artifacts become audible in this setting.
I’ll be doing some more experiments in the near future, hopefully.