Romney's a proven loser. That shit been writ. I think they might try and use Romney to spoil the nomination process and then toss him some phat lobbyist position but Romney ain't winning against Clinton or Sanders or Trump or anybody else.
The goob and I were talking about this stuff a couple-three days ago. His hypothesis is the Republicans run some Bright Young Thing in 2020 and bum-rush the middle. This article bears out his thinking - this is A True Scotsman arguing that 2020 ain't near soon enough and that nuking this election in order to build a base from which to launch 2020 is time and effort well-spent. From that perspective, if they could talk Nikki Haley into running Dixiecrat-style they can almost guarantee that Team Drumpf wastes salvo after salvo after salvo on who she is, not on what she says or does and that only disgusts the few brown-shirts that they might be able to bring back into the fold. Clinton (or, there's still a possibility, Sanders) won't really have any reason to say shit about a rear-flank attack, leaving Haley well-positioned for any future run. She's young - assuming she doesn't blow herself up, she's probably got 30-plus years in politics so it doesn't really matter how she does.
Most importantly, though, "they" could try any and all of this because "they" have lost the script and there are all sorts of factions trying to figure out what the fuck to do. When even the Koch bros are keeping their powder dry, we can expect an electoral season of much improvisation, methinks.