I think heists will be done in free roam, or at least some of them. You ever see one of those Fleeca banks with the really detailed interior but you can't enter? Those are ALL over the map, and you can even enter a few in sp. I think it's going to be a lot like robbing a gas station. Go in, blow the safe open, and fight off the cops. ( they have a really simple interior design btw, so it wouldn't surprise me if this is all there was )
Those places should have been opened up from the very start for free roam, they could have been mini-heists.
For the how I think they should be, see my post here: http://gtaforums.com...uld-betrust-me/