I am convinced that you are right about the bishop/flying sparrow being too powerful, even early in the game. I think it might be wise to have the demoted value as something similar but weaker, with a short-range bishop move. Like the mountain dove from Taikyoku shogi would have a move just like the flying swallow when translated to the 1D board, but would limit it's forward movement to 5 squares (10, if we're including the skipped squares). That's still pretty far, but maybe a little more searching would yield a better piece.