Well it would be historically accurate if the monuments were in their respective counties. Also I only mentioned those three because they're the ones I thought of while typing the post, and finally how are they not balanced?
I meant balanced against each other.
Some bonuses to papal relations and religious vassals doesn't really balance against reduced revolt risk, bonus levy, bonus intrigue and bonus martial. That last seems enormously powerful, especially for one building.
In addition there isn't really anything demanding that the capital is the "historical" one. It's plausible for England to be governed from almost anywhere, but York is a strong contender. You'd be punishing the player even more than the current situation for having their capital elsewhere and possibly letting an AI duke build these instead.