I do not think it needs to be able to capture its own pieces. In fact that is its weakness, no capturing your own pieces! But, perhaps add a rule allowing your own pawns to capture your own mamra.
I looked at the ZRF codes, according to that, pawn can promote to mamra. However this page does not mention it. Perhaps it should be mentioned in this page.
Another idea is to allow mamra to capture mamra, but if done so, both mamra are destroyed and also all adjacent pieces of any color are also destroyed. If any kings is destroyed in this way, whoever's king is removed from the board is a loser.
I do not think it needs to be able to capture its own pieces. In fact that is its weakness, no capturing your own pieces! But, perhaps add a rule allowing your own pawns to capture your own mamra.
I looked at the ZRF codes, according to that, pawn can promote to mamra. However this page does not mention it. Perhaps it should be mentioned in this page.
Another idea is to allow mamra to capture mamra, but if done so, both mamra are destroyed and also all adjacent pieces of any color are also destroyed. If any kings is destroyed in this way, whoever's king is removed from the board is a loser.