would it not be much simpler to make the sandbox mode a limited version? for example, heroes of the storm allows you to play any hero in the store for as long as you want for free in a limited sandbox mode. There is ZERO sense of reward after playing and nobody could possibly just play that without having to partake in the real thing. Any limiting factor would fine i think. For example, it could be bots only, or it could be 1v1 bots only. it could be multiplayer but have a really short time limit, where most games never even complete. Anything to make it not fun enough to play regularly so the only reason you would go there would be to test something...which is why sandboxes exist. i dont see a reason to pay for its use. i mean if subscription is what riot wanted to do, then just change the business model and make the whole thing a wide open pay to play game.