Thank you! So much fun.
I've found a bug regarding Saboteur. See this snippet from a sample game:
BM - Saboteur(Plr 2) plays Saboteur
... MEGA turn(Plr 1) reveals King's Court
... MEGA turn(Plr 1) trashes a King's Court
... MEGA turn(Plr 1) gains a King's Court
I suspect it's a lingering effect from the Quarries played by MEGA turn previously. If these cost reductions aren't only made in the appropriate buy phase that might have other bad consequences as well.
Speaking of the included MEGA turn I don't understand the extra_operation type="plus" attribute="11.0" part of its buy-4-provinces-rule. A constant plus a constant is still a constant, and 32 seems like the relevant thing to compare to anyway. A mistake?