Since you're maintaining class definitions per object, perhaps you should just move the classes into the object.

By the smell of it I'm guessing you might want to look at classless objects on the CPAN.

There are many implementations, many of which have a nice edge on the issue. I particularly like Class::Inner for what it's worth, which is a bit of a hybrid. I think it may work well in your scenario. Skip my module though - I believe it won't be useful in this context.