I agree with the thrust of your argument -- that Trump is more about expediency that ideology -- but I look at it more in terms of his perception of profit and loss. I expect him to do what he thinks will gain him more adulation from his fans and punt the rest.

If left to his druthers, I have no doubt that Trump would bail on building the wall, prosecuting Hillary, overhauling Obamacare and probably most of the rest of what he promised. As you point out, those things would take too much effort for someone who really only cared about them as campaign issues. 

But Trump has an irritable constituency to feed, and he knows his legacy is cemented to how much red meat he throws them. He has to quickly deliver on some of the scorched-earth promises he made -- and not just the easy ones -- or he'll lose the half of the country that isn't already revolted by him. It's hard for me to imagine a narcissist like Trump letting that happen.