Please add a feature that will let you be able to sell kits or at least trade 1 kit for another. The trades could be something like, trading "Scout" for "Enchanter". If you are going to trade, You can only trade kits with the same price. I am suggesting this because I've noticed that a lot of players are accidentally buying wrong kits. Of course, there should be a limited time for you to trade a kit for another one. Maybe like... you can only trade this kit for another one within 20 days of having the kit. You can no longer trade that kit for another one after 20 days of having it. The kit that you got after trading will not be available to trade because that may lead to abuse.
This will mean you will only have to buy 3 kits (1 for every level of xp costs). If you want to use a kit just trade it for another one you used last game and so on.