Could there be a button or a command that prevented the pokemon from earning exp?

This would help very much in organizing tournaments or duels as there could be a special team that player has that they duel with and have no fear of being over-leveled.
As it is currently older players will stop new players so they won't be able to participate. If there was this function all players could build up teams and keep them at let's say level 25. This would also incentivize catching more versions of the same poke to work on different combinations of evolution stats, thus spending increases lowering inflation of the game's economy.