I see 3 ways of balancing it , each a bit different :
1) -2 speed, + 1-2 k price. Makes it the second best cavalry sword after Arabian Cav.
2) -1 speed, -1 cut +1-2k in price. Weapon will be in between nordic champ and knightly arming.
3) keep the speed, -2 cut , - 1 pierce , +1k in price. Would be a mediocre damage elite scimi upgrade with decent stab. Kind of a meh option tbh.
3.2) keep the speed, -1 cut, -2 pierce , +1-2k in price . Same as above, just less pierce instead of cut
# 1 is still my personal preference, i'd say, or #2.