I am not 100% sure what you are aiming at and since I have been asked something similar yesterday:
Sure it is and will be possible to use a panel class in a different app, just like it is possible with screenbar modules or even any class you find peeking and poking in any code running at time.
Thats offcourse a dangerous idea and doesn't make much sense in the 1st place.
As for being able to subclass panel classes to change look layout or behaviour, sure thats about 90% of what this update will be about.
So there will be panel app (not an mcc) which provides the basic classes which you will either to able to subclass or replace with your own MCCs. If you want your panels to look like the Windows start menu or maybe even the Win8 tiles, if it shall look like early OSX or if you want to mimmck the look of same fake made for TV OS. All is possile.
None to little of that will be part of the default app included in MorphOS3.28 and upwards ;)
