>How to subclass group classes, so they will contain my classes as members? Ex:
1. Formset

There is no easy way to make a formset default to a different base form class for forms added by adding a form.

You can, however, use drag and drop to drop forms onto the formset from a project.

BUT ... IMHO you would be better off dropping the use of formsets all together
there is really little need for them in most circumstances.

2. Pageframe
This one is also tricky ... again you cant override the default page.