I'm for a system where you have to go out in the wild to initially tame your beasts (I like the tamable NM idea), but once you have one of a particular family, it is yours to summon whenever. I almost want to say a beast should share the beastmaster's level, but I'm not completely sure about it. Optionally, they could allow a limited number of beasts owned per player (6 to 10?), so in that case they'd have to also implement a release feature. Although, I can't see that being an issue unless it's too limited (2-4).

One thing is for sure. I never liked jug pets. Terrible idea, imo.