Hmm. How about -
Arcane Undead Rebuke/Turning (pre-req: Either a specialist necro or abjure). User must spend a spell in order to turn undead - using the spell level (of the spell sacrificed) instead of their CHA modifier for that turning. So, a 8th level wizard goes to turn undead, sacrifices a 3rd level spell, and so turns (at his level) at 8th with a +3 modifier (as if 16 CHA). Use of this power provokes an attack of opportunity. If you are a necromancer spec, rebuke, if abjure, turn.
Perhaps include/allow bard to take it, but it also uses up a song, no specialty requirements.
Just a thought.