You know, you'd be surprised! I vividly recall owing storybooks and the like that featured pictures of Biggs at Toche Station, Luke using a blaster canon in Echo Base and Vader facing off against Royal Guards on the second Death Star.
Then there was the 'Behind the Magic' CDROM (which I still have somewhere), released I think in '97 or '98 and that had a whole load of cut and alternate footage. The Irish Jabba footage, some of the alternate Cantina footage before the re-shoots (yes, they re-shot things back then too!) and of course the Toche Station footage!
I honestly don't think there were all that many alternate scenes vs. deleted. I think most of it will be the briefing scene since it set the tone somewhat differently and possibly some of the death scenes.
Yeah but that's Vader post ANH. This could be Vader post RotS, which is an entirely different animal. Still hip deep in blood, hunting down Jedi stragglers & Seperatist hold-outs, maybe even training the first Inquisitors.
Like I said though, if it were me, I'd wouldn't do it from Vader's POV but that of whomever he's hunting. Again, not my first choice (*couch*Kenobi Movie*couch*) but I think it could work with the right script.