I agree with Freyar that a rejuvenation ability would be good. There should also be some way to prevent this from happening (slay him on his home plane? cast holy word and dispel evil on his corpse within 1d4 rounds?)
Feats-wise, Power Attack seems like a given for a bruiser like this. Cleave's nice, but not really required. Quicken Spell-like Ability could be good for either fly or suggestion. Improved Initiative, Multiattack are both solid. I'm tempted to give him Improved Bull's Rush + Awesome Blow + Combat Reflexes, so he can smack people who are in melee with him, then grab them with his tail when they try to close.
My vote for final feats? Awesome Blow, Combat Reflexes, Imp. Bull's Rush, Imp. Initiative, Multiattack, Power Attack, Quicken SLA (either fly or suggestion).
Demiurge out.