I'm with Maximuuus and Pipboy. Think about the outcomes from a player perspective and either way it's ripe for frustration. Either players will waste their time fiddling with Larian's already lacking item management systems to make the most of the bonus, or they ignore it and are missing out on the potential bonus and are aware of the bonus they're missing out on, for no other reason than the system is poorly designed. The role play potential is severely lacking as well, since as has been pointed out, tying reputation to individual characters doesn't have the desired effect when the assumption is that the party will travel together and so will always be selling stuff together. With this current system you get a situation where a hated character can just hand off their gear to their friend while still with the rest of the party and that doesn't impact anything at all.
And if you wanna go deeper, then what makes more sense on an RP level? The party all loading up the character with the best charisma, stepping back and letting them negotiate with the merchant who witnessed all that, or having the characters together and letting the most charismatic character schmooze and do their thing as each other party member presents their items to sell?
