A suggestion for Veigar's R

If suggestions like this are still open, I think this would be suitable for his new kit. It would be a passive ability, that only triggers after all three abilities have hit a single target. Either instantly, or on the next basic attack, a compression of dark matter would explode on the enemy, dealing significant damage either rivaling or close to rivaling his current ult that would deal AoE damage to all enemies around it and/or stun them. It would still have cooldown after use of course. I'd assume it would use mana when triggered. What do you think?

Oh and while I'm here I think his passive ability should be changed and compensated for by a Q that returns 50-100% mana when gaining ap stacks. The amount of mana returned should depend on the AP gained.