Engine naturally, but I'm quite skeptical of the Remodel opening. You won't really be able to use it on your coppers, so its ability to thin you is limited. Gains from it are nice, but it has a high opportunity cost on two levels:
1. When you buy it, that's a $4 that could have been Ironmonger.
2. When it's in your deck, you will sometimes dead-draw it with Wharf. More consistently, you will simply have too few actions to play both Remodel and Wharf in the same turn. If you don't play Remodel, it's actually clogging your deck up, not cleaning it. And if you don't play Wharf... I think we all know what happens there.
Trashing comes first in most cases. If there were a trasher like Develop or something that could actually hit coppers without feeding you estates, opening it would be a clear move. Remodel, though, is only good at trashing things with a cost higher than 0.