They still have to level their Beastmaster to cap (not just to 45) in order to make full use of the subjob, so I think that balances out. Anyone who has gone through 90 levels on beastmaster and then goes RDM/BST or DNC/BST is still a beastmaster in my mind.I also think you guys might be missing the point. The problem with charmable mobs is that, due to game mechanics, other jobs are better BSTs than BSTs at high levels. RDMs, BLMs, NINs, DNCs, even CORs that solo things in Abyssea could go /BST and throw charmed pets at NMs to supplement damage. They'd be more effective than BST mains due to the other tools at their disposal. As it stands, jug pets make BSTs unique.
With the addition of strong jugpets, though, that's a moot point. A charmed mob is strong, but the new Jugpets are nearly as strong, and the BST has greater control over it's behavior than a /Bst with a charmed pet. All in all, I think it balances out. Beastmaster is one of the few jobs I think they got right when it comes to subjob use, at least before Abyssea came around.
Although I wouldn't mind seeing some weaker jugpets that were All Jobs equipable..