Seems to me the obvious thing for the GOP to do is try and appeal more to black voters. If they got the numbers to 70-30 D or something, then they flip back Georgia and maybe Texas. Also, LOL at suggesting NY and IL could flip back before GA or TX. I mean, I'm bullish on trends and everything, but the numbers just aren't there. Clinton basically tied among whites in NY, IL, CT, and MN, so the GOP would have to win back whites and/or actually flip minorities, which just isn't happening.
The GOP actually could make inroads with all demographic groups if they moderated on healthcare, housing and infrastructure actually and if they did that they wouldn't need to use divisive cultural issues as much to get WWC to vote for them.
And the Democrats could similarly make inroads into Appalachia if they ditched their guns and environmental planks of the platform, but pretending like either of those things is ever going to happen is wishful thinking at best. So don't get your hops up on the GOP changing anything about their economic/healthcare agenda anytime soon when Trump of all people couldn't manage to do it despite campaigning explicitly on those things.
The Republican elite has no interest in any of those things ever happening, which is why it will never happen. Republicans won't go against their donors.