Has anyone suggested Picard remaining Locutus of Borg after Best of Both Worlds?
I know that pending the cliffhanger, there were a lot of rumours that Patrick Stewart wasn't returning to TNG and that Riker/ Frakes was going to take over as captain. Had this happened, Picard/Locutus/ Stewart could have returned occasionally as a villain - indeed, some have suggested that he might have made an intriguing villain for First Contact.
The main problem I have with this is that I love the character of Picard too much to have written him out like this. And I don't think the subsequent few seasons of TNG would have been such a big hit had Riker/Frakes been the lead. I certainly can't imagine that the show would have been successful enough to lead to movie spin-offs; he's much less of a leading man than Stewart, IMHO.