I understand your points. If there was 1 BN on b1/b12 and 1 RN on k1/k12 only, all your specs would be respected: all pieces can move behind the lines, all pawns are protected, the Cannons keep their mobility.
This setup leaves an empty space on a1 without any piece able to move to it, which adds an element of arbitrariness to the setup that I don't like. It also reduces the usefulness of the Cannon and Vao by giving them fewer valuable pieces to potentially pick off, and it removes the chance of a Vao threatening to eventually capture a Rook or Marshall along a diagonal.
Just there is no symmetry for BN and RN, but there is no symmetry for Queen either and this is not illogical.
It increases the asymmetry in the game, which I prefer to avoid.
I have understood that the reason why you had 2 BNs,2 RNs is because you owned 2 physical Gothic chess sets. An option to play with a single BN/RN set would be worth to consider maybe.
If we did that, it might work better to put the Archbishop by the King and to put the Queen and Marshall in the corners. Since the Queen is more powerful, it could go on the Kingside corner. This would take care of some of the objections I had. However, I would otherwise prefer to keep the Queen by the King, which is the more traditional position for this piece, and having two Marshalls and Archbishops better accommodates this.
This setup leaves an empty space on a1 without any piece able to move to it, which adds an element of arbitrariness to the setup that I don't like. It also reduces the usefulness of the Cannon and Vao by giving them fewer valuable pieces to potentially pick off, and it removes the chance of a Vao threatening to eventually capture a Rook or Marshall along a diagonal.
It increases the asymmetry in the game, which I prefer to avoid.
If we did that, it might work better to put the Archbishop by the King and to put the Queen and Marshall in the corners. Since the Queen is more powerful, it could go on the Kingside corner. This would take care of some of the objections I had. However, I would otherwise prefer to keep the Queen by the King, which is the more traditional position for this piece, and having two Marshalls and Archbishops better accommodates this.