It's mainly the "only 3 crafting classes can get specialization recipes" part I disagree with (and even more so the OP's requests for even more exclusion). With DoW/DoM jobs, we don't have to select which 3 we're going to specialize in and only those can get certain skills. We're allowed to play all of them if we want to, and they're all allowed to advance all the way to endgame with every skill and gear available. There's no built-in requirement that all your secondary alt jobs have to be held back as more limited than your main, and there shouldn't be for crafting classes either.
In the other direction, I also think 50 is too high a level for essential cross-class skills. Of course, at this point, it'd be pretty hard to change the level of those skills and re-balance everything, but maybe Kenji's suggestion of making them natively available rather than cross-class would be good, at least for the level 50 ones, and perhaps CUL's level 37. Needing to get everything to 15 isn't bad, so those ones could be kept as cross-class. And the elemental skills at level 37 are insignificant enough to not really generate an omni-classing requirement. It's mainly just those level 50 ones that create a huge leveling hurdle for a casual game.
