Getting account XP for TFT makes sense if the rewards change based on what you play

Right now I really want account XP for TFT, but I fully recognize that it doesn't make sense to get rewards (champion capsules) when that affects a totally different game. So, why not change the bonus from champion capsules to something else? Right now there's nothing to change it to, but it makes sense that green essence or something is added in the future, and usable to buy maps, LL, or other things similar to blue essence. Perhaps what you are rewarded with when you level up is based on which game you play more?

That would at least continue to keep account XP as properly showing how much time is spent on that account. It would also allow a way to more easily earn rewards and price bonuses in the future.