Has there ever been consideration for voice reworks without VU?

It's happened before with Ashe, Anivia, Xerath and Sivir if memory serves. Very few times but it has happened to varying degrees.

Short Answer: No.

Long Answer: Probably not. With how rework happy Riot's been the past two years, they'd likely just wait. If a champ's VO is outdated, chances are their visuals and kits are too.

MF is one of my favorite voice overs in the game..

She needs a VU.