Hussar
Legend
But, that's the point. Why not? Granted, Disguise Self is an illusion, so, that's out. But why not a modified Alter Self (no adaptations, no natural weapons)? Make it concentration with no duration. Poof, now, it's nice an flavorful - but, changelings are vulnerable when they sleep - they revert to their natural forms. Because it's straight up a spell, it's detectable, dispellable and no longer bypasses the limitation of casters.Oh, I don't think they never should be, but I' don't feel making every remotely supernatural ability a spell is good either. I would hate, for example, to replace a changeling's ability to morph into other species just become "cast disguise self x/per day" even if the two have roughly the same parameters.
But I get you don't like the idea that characters have abilities you can't hard block.
Those limitations on there on casters for very good reasons. By making obvious spells "non-spells" it's just power creep.