LOL, OSR is such a Romney fanboy. No Romney would not win by 15 or 16 points, this isn't 1984 and he's not Reagan. Such landslides are impossible for anyone now, let alone a Republican (and such an uninspiring one to most at that) in our polarized, D-leaning electorate. If he won at all, it would be narrow. He probably would not win D-leaning states like Minnesota, Colorado, Virginia, Nevada, or New Hampshire (another OSR fixation). And the other swing states are debatable at best.
I think Romney probably wins VA and CO if he won in 2012 and I don't see any reason why he couldn't win them again in a successful re-election bid. I'm not a great fan of Romney but realistically if things played out roughly the same between 2012 and 2016 roughly as in our real time and the economy still gets more back on track, I think Romney probably wins re-election. There is a chance someone like Bernie comes along and upsets him but in a scenario where the economy's doing well and Romney hasn't made too many mistakes abroad/at home a Bernie upset seems unlikely. Don't forget Clinton isn't a great candidate either. If she couldn't win against Trump, I don't think she does well against an incumbent Republican unless said incumbent messes up badly.
I don't t think Romney wins MI but I think he would win the latter 4 states you mentioned. (along with WI, ME-02 and PA) Looking at it, I'd probably leave NM narrowly with Clinton. I'd still expect a 322-216 win for the president though. Wisconsin in this scenario would probably be pretty close but I think Ryan would tip it over. Romney still wins 312-226 even without WI though.