Thx for all the feedback!
The core problem we're trying to solve is preventing access to higher level skills at lower levels, and reward specialisation while still allowing you to play class free.
The current idea is that requirements solve the former problem, and giving you access to (more) spells in a school + "something extra" takes care of specialisation rewards. We didn't do the "something extra" yet and there's certainly room for debate on which requirements we use on what. It's also unfortunate that the skills are now random at traders. As such, the new system can be improved a lot and will probably yield something that works well enough.
But, that doesn't mean that we're not open to suggestions that achieve a solution to the problem we're trying to solve. If somebody posts a better idea here, we'll certainly consider it.