If the Belt of F/M treated every NPC like Edwin (gave new voiceover and dialogue, portrait and paperdoll), but you could use it only on a single NPC, who'd you give it to?

A theoretical. I often use the Sword Coast Keeper (pre-EE BG1-compatible Keeper variant) to cover the portrait and paperdoll parts (though sadly not voiceover or dialogue), so I kinda have something like this going rather than treating the Belt as one-off inconvenience.

Some of my more serious picks would be Kivan, right after finishing his revenge — by way of symbolically and literally turning a new leaf as a person no longer bound by her past as a married man; or Safana, for a reverse Edwina character growth scenario — from a capable woman playing up her weakness to charm and hoodwink men into serving her needs, to a self-sufficient swashbuckler-pirate-looter hero she almost is if not for her reliance on others (a form of self-perceived weakness).

A less serious nominee is Yeslick, so she can start working on the most vital task of her life — repopulating her lost clan.