Account Bound progression is really the only way to go with this, unless you want people to feel forced into playing only one character, which, in this game, is really just not a good idea considering you guys are making money off people wanting to play more characters. There is no reason behind making it character bound, you may think “Oh but it adds progression, something to be proud of” but the community sees it more as “I’ll log to my other characte- wait, no that character doesn’t have these bonuses, I’d be better off just staying on this character”