The number of lords wouldn't necessarily have to be limited, it would just have to be limited to their playstyles. Marth and Ike would fit in easily, and then you could round off different fighting styles with Ephraim and Hector. The Lord classes are very varied. You've put 4 slots there so that kind of works.
There could be different types of mages. Micaiah or Lucius would be a light user, etc. Could use some villain as a dark magic user, and just about any mage as an elemental magic user. It would be a simple matter to give the attributes distinct styles (Light as burst damage, elemental combo oriented, dark zone control)
I don't really have anything more to say about this tbh