Every non-populist, non-religious right candidate would've won it without too much of a problem (so, Kasich and Rubio would've carried it easily). A religious right candidate, like Cruz, would've been a 50/50 shot, and it would've depended on the vicissitudes of the campaign. A populist candidate could not have won.
None.
Beyond OH and IA, Trump, and only Trump, had the ability to expand the map.
Only Trump had the power to win MI (and
probably PA as well, but I'm less certain of that; Toomey 2010 margins in NEPA and the hinterlands combined with 2016 margins in the Philly burbs are a plausible non-Trump path to victory, but I don't know what non-PA Republican, besides maybe Kasich, could've pulled that off), but CO/MN/NV/VA were all winnable for a different sort of Republican (and even among Trump's states, WI could also have been won by a different Republican, though the coalition would've looked very different from Trump's, since they wouldn't have gained anywhere near as much in the rural west of the state but would not have bled in the suburbs like Trump did).
Kasich could've gotten this map:
