From the perspective of getting a V.P. who will help him work with Congress, Kasich is probably the best choice of all the other people running. Trump might need that given his inexperience dealing with the basic checks and balances of the government and the grunt work of things like counting votes.
As long as Kasich is willing to sign onto all of Trump’s agenda, then I don’t really see what the problem is with him. It’s not like Bush, Sr. was a detriment to Reagan as V.P. Of course I realize this doesn’t “set up” a conservative to become President after Trump, but they still have a chance in the primary. Obviously being “set up” as V.P. didn’t guarantee Biden the nom in his party.
The problem with Kasich is that, like almost everyone else, he’s a liar.
Whether or not we win an election by electing a liar simply doesn’t matter, because by electing a liar, we lose.