Make it more realistic and allow no more than 25 players in every team i.e. a maximum of 10 subs! This will allow for a cover player for every position (1-3, 2, 4-5, 6-7, 8, 9, 10, 11-14, 12-13, 15) in case of injuries. A beneficial side effect would also be that teams would have to use MB more sensibly to avoid too many injuries.