[Idea] Tag out

The new gym system requires your Pokémon to be kicked out of the gym for you to get your coins. Often you end up seeing your Pokémon stuck in a gym for days, which gives you zero coins.

What if you could mark your Pokémon in gyms as "tired". (Or something like that. ) This would make it possible for trainers on the same team to replace your Pokémon with theirs. The gym wouldn't lose strength and you have the opportunity to collect those sweet coins.

Tl;dr Mark you Pokémon in gyms to be ready for tag out. Other trainers from same team can tag in. You get coins, the other trainer gets a gym spot.