I can't decide if Trump is an idiot or a genius. Let's roll with the genius theory for a moment.
Since the early 1900s, the Democratic party claimed to be the party of labor. In the long-run, from a political "currency" standpoint, it's a good idea to have labor in your pocket. For the last... eh, ~35 years the Democratic party has only paid lip service to labor while stabbing it in the back. During this past election, the Democrats had a chance to run either a guy who walked the walk or a woman who was notoriously well connected to large, multinational corporations. They went with the latter. Trump saw an opportunity (I think) to pry labor away from the Democrats and totally rewrite the rules for future elections. If he actually follows through on his promises to protect American labor (sort of the point of Nationalism) he/the GOP can hold that up as an example of an impotent and duplicitous Democratic party.
Look, I grew up in Chicago. I've seen how unions "work." I'm not a fan (caveat: I fully understand their importance in balancing the power of capital in theory). However, if Trump has to cozy up to them to turn a bunch of blue states red I'm fine with that.
Personally, if I were advising Trump I'd have him set up shop in Flint MI and torture the Democrats into a standalone emergency appropriation bill to fix their water system (even though there are 1,400+ municipalities with higher lead levels in their water). Do it for the optics alone. Show that you actually care about the state (even if you don't) and they'll love you for at least the next three elections after decades of being abused by the Democratic Party. I'd then tell him to go to Pittsburgh and do the same thing to request the necessary authority from Congress to renegotiate NAFTA. Hold rallies in the area, tell them how China abuses the country of origin rules to smuggle in steel and aluminum duty-free and how corrupt Mexican politicians are complicit in fucking them (the steelworkers and their families).