For now, I just finished adding the Black Market to Steadwick sewers, where you can buy and sell stolen items:
House animation is from the (unimplemented) Nighon bank. I don't like the glowing eyes, but otherwise it's close enough.
The plan is to also have it replace the Judge's "I lost it" feature, but this would require tracking quest items more thoroughly, otherwise the market ends up crammed with every trinket currently in your castle's chest. If I do implement that, it will organically fix the book of Divine Intervention exploit (which can be duplicated and sold in vanilla), since you'd have to pay money to get it back from the market, eliminating any potential profit. Hopefully I'll get around to this.