Also, assuming there's even theater support, will we be able to rewind campaign footage?
Halo 3's theater might answer this question, or at least give decent clues

And will ODST be integrated into the existing party/menu system, or will it be a separate menu? It would be awful suspicious for there to be hooks built into the game if the game wasn't planned to be paid DLC from the start...

Which reminds me, since ODST used Halo 3 assets, will this be true of the Remaster as well? It might cut down significantly on file size, but if that's not the case, could ODST be released as standalone DLC (similar to Infamous: First Light)?

I'd definitely buy a remastered standalone ODST, even if I only got to play it occasionally on a borrowed Xbone...