I've given this some thought, and there's two ways to go about it.
The first is that we create a vote power system, which would allow the host to update vote weights before the player casts a vote...the benefit to this would be that the vote power would immediately be shown on the tally when a player makes a vote, but the downside is when the power can't be determined beforehand, such as if a player can steal a vote as they're voting themselves. In that case, their actual vote still needs to be modified by a host to reflect their vote power, and until then the tally may be misleading.
The second is for hosts to be able to modify players votes directly to add the vote power, but this removes all the benefits of being able to specify vote power beforehand and will mean the tally may often be misleading unless a host has just updated used vote powers.
The long-term solution is to go with a vote power system, but it needs to include an option for hosts to specify if a player has the ability to steal votes, if they have so many times they can add or subtract votes, and things like that...because those are largely determined by the players role, it wouldn't be appropriate for me to be privy to those details as a player (assuming it's being used at all in this game), so actually building this system will probably wait until the next game, especially if someone has an idea for using this. That allows more discussion on the idea in the meantime anyways.