While it's true that death isn't really stopping old Middy, as the progenitor of all dragonkind he's probably got special privileges (being able to strip us of Hydaelyn's blessing, resurrecting dead dragons as phantoms during the fight with him, etc). The Wyrmlords / Celestial Dragons are definitely more powerful and long-lived than your average dragon, but as Middy's kids they probably aren't as powerful as he is and can't do all the things he can, though they might have some tricks of their own (Nidhogg being able to influence people through his disembodied eye, f'ex).
That's not to say Bahamut couldn't be corporeally resurrected as Middy was, but we'd need at least his spirit, some aether, and to know exactly how Middy created his whelp minion form if we wanted to do it ourselves.