I think the only way a loan system would work is if the duration of the loan was done via games - I.E. a 3 game loan - which would cost 3 Tokens. A 5 game loan would cost 5 Tokens etc...

Doing them for a season would be counter productive in my opinion and you would see peoples second accounts simply loaded with loan players from their first accounts that would be far superior to what you could have if you had to own the player outright.