Have you read Eric Silverman's thoughts on poweful pieces? He suggests that it's good to have a few super pieces that dominate the game.
When you say "larger boards" it's not clear if you're talking about the later mentioned 10x10 CWDA or something else. 10x10 doesn't seem large, and you did use the Joker on 10x10 and 12x12 already. If you are talking about something truly larger than 12x12, the obvious way is to have the Joker start at the back and make sure the average piece strength isn't too high.
If you're worried about the Joker dominating the game by being too powerful, don't forget that if it's really that strong the players would be reluctant to trade it away. In that way, strong pieces can be self-balancing.
I could imagine it possibly being a problem if the Joker loses strength quickly so that there's a large advantage in deploying one's Joker first, which would naturally favor the first to move. If that is a problem, a way to counter it would be to carefully choose the moves of the other pieces. Perhaps have more sliding or other blockable moves instead of leaping moves, to allow for pawns to reveal attacks on the Joker by weaker pieces that could be exchanged for it. Another way is to make sure that pieces have simple moves so that a player would be likely to have good options that limit the Joker.
Have you read Eric Silverman's thoughts on poweful pieces? He suggests that it's good to have a few super pieces that dominate the game.
When you say "larger boards" it's not clear if you're talking about the later mentioned 10x10 CWDA or something else. 10x10 doesn't seem large, and you did use the Joker on 10x10 and 12x12 already. If you are talking about something truly larger than 12x12, the obvious way is to have the Joker start at the back and make sure the average piece strength isn't too high.
If you're worried about the Joker dominating the game by being too powerful, don't forget that if it's really that strong the players would be reluctant to trade it away. In that way, strong pieces can be self-balancing.
I could imagine it possibly being a problem if the Joker loses strength quickly so that there's a large advantage in deploying one's Joker first, which would naturally favor the first to move. If that is a problem, a way to counter it would be to carefully choose the moves of the other pieces. Perhaps have more sliding or other blockable moves instead of leaping moves, to allow for pawns to reveal attacks on the Joker by weaker pieces that could be exchanged for it. Another way is to make sure that pieces have simple moves so that a player would be likely to have good options that limit the Joker.