P.S. Pence is the favorite to succeed Trump and should unite the GOP behind him. Just wait. 
Agree with 80% of what you said, but Pence is the wrong person. His schtick is being really socially conservative; economically speaking he's fairly establishment. To move that direction GOP needs a Keynesian who can go the socially-conservative route without alienating Hispanics or African-Americans as much as Trump has (both relatively socially conservative groups who vote D simply because of endless and unnecessary dog-whistling from the GOP). Can't think of any major figure who fits that bill though.
You can't just have a GOP with zero regard for the business community, the well-off, budget hawks and other economically right-of-center folks. The "Establishment" (to the extent that means anything) certainly made a mistake thinking they only needed people exactly like them to win; the "Trumpists" (again, to the extent that means anything coherent post-Trump) shouldn't make the same mistake. As NC Yankee has said, the future of a winning GOP involves an economically moderate party that is much more socially tolerant than the current Republican Party, one that neither repulses voters that have supported the party for a long time (like Trump has done to many Republicans) nor makes swathes of Americans feel "too poor" to vote Republican (as Romney somewhat did). We need a big tent.
Agree in principle but it's not the way the party is moving. I think the state of the GOP tax plan is proof that there are very few 'economic moderates' left there; the WWC-types are beginning to realize that the R establishment isn't doing anything for them. For what you describe to come about, the GOP would have to eject both its economic-right and social-right extremists in order to rebuild an old coalition, rather than ejecting just the former to build a new one. It's happening anyways, just look at Republican favorability of Ryan and McConnell over the last few years.
Color me skeptical that the majority of Trump's voters will get on board with "Keynesianism".
Considering how republicans were quite willing to support Reagan and Bush 43 I don't think they'll have too much of a problem supporting Keynesianism.
