Haha this is going to make people diablos further, but the only way they could make it work would be to do it right now. The good thing for them would be that Trump has no campaign or good fundraising efforts. The only way this would happen would be if he somehow dropped into the 20s and his support with the base fell off a cliff. Luckily republicans will continue to support him.
even if rubio or kasich want in, they're not going to excite the base. kasich might make a real good case against ohio and maybe pull in iowa as a result, but i don't think that also means he gets pennsylvania or even florida.
rubio could get florida i suppose. i don't think it means getting ohio in that case, unless these guys make a deal where kasich is the frontrunner and rubio is the runner-up.
and then i guess you'd have the koch money start funneling in, but they'd still be extremely behind on fundraising and especially behind on organization. i just don't think they can kickstart or whip up interest in such a short amount of time. i also think you'd still have a lot of support behind trump in a sort of 'trump or bust' movement.