I feel like going for an FV-Rabble draw engine makes Possession unsavory for the opponent. He can use FV himself to counter, but chances are he won't have all that many if he's dipped into Potions, and he may not want to play your Rabbles to junk up the top of his deck, especially if he hasn't trashed his Estates. Alchemist can try to draw through the clutter, but without an FV in hand, it has a greater probability of interrupting his Alchemist stack.
DG's appraisal of the kingdom is right, though; everything else can be a huge benefit to your possessor. In my opinion the acceleration provided by remodeling Estate -> something better is a little too good to pass up when building an engine supplemented by Rabble, and you'll just have to bite the bullet and hope that it doesn't work against you too much later on or hope that you can Island away the Remodel before your opponent gets to use it.
Another option that I see is to build an Alchemist engine, grab a couple of Possessions + FVs, and then Mint away enough treasure in your deck that you can't make $8.