Gift of Gab wouldn't be too hard I think.
Just in the current UI, similar to how you can add bonuses, have a box that possesses the things that may allow you to reroll, such as Lucky Feat, Halfling's Luck, and in this case allows you to spend a spell slot to reroll a Charisma check in a conversation using Gift of Gab.
Well it's about changing the character's memories, and resetting a social interaction. I don't know if it's the highest priority.
(And I intended for a different choice of words, but it's hard when you're focused on recalling all possible reactions).
It still doesn't impact combat, so it shouldn't be an issue for multiplayer.
