Jim,
your question:
quote
I occasionally run into the situation where I have used the class designer to create a new class by subclassing another class. Let me call the new class Class-A.

I then use class-A in another class, or in a form.

I later decide that I would rather use class-B in that class or form. I don't see that VFP makes it easy for me to change the class of an object in a class or a form.
unquote

I believe I misunderstand, but what I read you have changed your mind not to use class-A but rather class-B. So what's wrong with deleting class-A from your form and implent class-B?
Do you have a problem with deleting an implented class from a form?
Regards,
Koen