Maybe I am out there, but I think all the early comments are missing the point.
I think lucky one is right that you should build a wharf semi-engine here first, and then pick up a steward for trashing and a witch later. Wharves don't mind coppers, so you only really want the trasher for estates and curses. And with your engine going, you can trash those pretty quickly. Similarly, I think you have a good chance of catching up on the curses race if you buy the witch a few turns later, but then you can play it almost every turn.
I think opening militia/steward is pretty bad here (and I am a big fan of steward openings). You really want to pick up that wharf (or witch if you disagree with my opinion above) on turn 3/4, and then you have three terminals with at most one village - and you hoped to trash some cards too! Opponent's militia also makes the early steward much less effective. If you want top open steward at all, I think it should be steward/silver.
I am really curious what others think.