We seem to be getting about ONE Bat-villain a year, so at that rate I'd prefer Penguin and Catwoman and Freeze over the next 2-3 years.
After that, everyone is a bonus.
I might consider Egghead... no on Bookworm, and as a kid I just hated King Tut so, in adolescent principle, I would pass on him too.
Mars showed Mad Hatter further long than any of the above and, despite him looking like Penguin in formal wear and Top Hat, for some reason I really liked him as a kid -- I found the hat opening to be creepy -- so it would be hard to say no if he was offered.