Try-out contracts
 

Since they are quite common in Europe (and sometimes happen in the NHL as well), it'd be really nice to have the ability to sign players to try-out contracts. After a set amount of games (let's say 4 - 5), you'd have the option to sign the player to a proper contract, or just let him go. It'd be also a great feature for teams that have a lot of young players, which have problems with setting line-ups during the World Juniors and such.