Well, currently the ID only supports Tamerlane II succession, which allows you to swap King and Prince in checkmate positions as a move. What it could support in the future is mainly dependent on how complex that is. Automatic promotion of Prince to King and removal of the latter as a side effect of moving in a checkmate position might be doable. It raises the question what would happen if you decide to move Prince or King, though. And King rescue would not be possible if the King disappears automatically on any move you do. So swapping would be closer to your original rule.
I am not sure what your motivation is for using such a complex rule rather than just taking the Tamerlane II succession, which makes it hard to propose alternatives.
Well, currently the ID only supports Tamerlane II succession, which allows you to swap King and Prince in checkmate positions as a move. What it could support in the future is mainly dependent on how complex that is. Automatic promotion of Prince to King and removal of the latter as a side effect of moving in a checkmate position might be doable. It raises the question what would happen if you decide to move Prince or King, though. And King rescue would not be possible if the King disappears automatically on any move you do. So swapping would be closer to your original rule.
I am not sure what your motivation is for using such a complex rule rather than just taking the Tamerlane II succession, which makes it hard to propose alternatives.