Don't forget that the Republican National Convention back in January decided to throw their weight behind Donald Trump. While the RNC technically has to recognize challengers if they win five or more states in the primaries,
they're throwing all of their money and resources behind Drumpf already, regardless of outcome.
What I'm getting at is that any challenger is going to have to run without any RNC money or support, including the PAC and dark/illegal money that typically comes with the RNC's blessing. Unless Kasich and some of those other challengers can find a deep-pocketed benefactor or two, they're going to be done pretty quick, all things considered.
Plus, let's not forget, most of your primary voters are your party zealots for either side of the aisle. Trump's fanbase pretty much consists of any GOP member that isn't a sane, rational actor, so it's going to be hard to get moderate Republicans out to vote for Kasich.
So yeah...I really don't think Kasich can do anything unless he runs as an independent. And that's going to burn any bridges between him and the modern-day RNC/GOP...