I don't see an alternative thread for Blade Runner yet, but I would suggest using the International cut if you're planning on regrading it, as it pretty much encompasses the American theatrical cut, and Scott always intended for that footage to be there. Historically speaking, for many years, that is the cut that most people would also have been introduced to on home video.

I don't know how you'd do the sound for the “happy ending,” though I guess you could track in the love theme from Vangelis Themes album (IIRC, this is the original track with the synthesized saxophone — I could be wrong) as I don't recall there being any foley in that scene.