"We're making an informally-specified, ad-hoc, bug-ridden implementation of half of CLOS"
That's what I thought when I was thinking about solutions for these problems :)
I think (1) could be solved simply by using redef on each polymorphic function : if car becomes polymorphic, just encapsulate the desired behavior in a new definition of car that will do the dynamic dispatch for you. If you want a specific version of car (e.g. the array implementation), just call it explicitly : (array-car x) .
