>If you created in instance of class foo, then were able to modify class foo in the class designer while that instance existed, then created another instance of class foo, the two instances would not be of the same object, plus the caching system would likely have to be all modified to allow this behavior, and it would be likely performance would suffer because of it. I see this thread trying to understand how classes are cached, but I haven't figured out why it matters so much, or if there is some ER or change of behavior desired for a specific/explained reason.

Well it would get worse though - if you modify one of the base classes while you're editing one of the descendent classes you'd essentially be working on an invalid copy missing properties and methods possibly...

My concern here would be for allowing access to the classes (even if READONLY which you can't do right now) and the simple fact that I don't want any chance of my VCX corrupting while it's being edited due to a system or VFP crash.
I'm not sure, but I think the latter has been addressed in VFP7 since I haven't seen any corruption due to VFP crashes (well, it crashes a heck of a lot less for one <g>)...