Just throwing this concept out here

[B0rsuk]

Alexti: Magic available for nations already become much more specific, because independent mages are much worse now. On top of it national mages of the same quality cost much less.
Discouraging using strange paths on pretenders would narrow available spells even further. Pretender magic is - for many nations - the only way to try something new. And you're pretty much required to have national Blood mages if you're to try blood magic at all. And it would harm bless strategies, too. Kailasa sacreds, for example, literally scream for Air bless, because they have little to no protection. But none of their mages has Air,even as random. Should they be denied a chance to try air bless ?
I think it's enough that pretender choice strongly depends on the nation. It makes some paths pretty hard to get, unless you try human pretender like archmage.