If you "really" want to make the balance leads the same length and make them visually appealing, you could just make them a little longer, and the furthest one have 1 loop, then would get an extra loop with each one closer to the unit.
Another option would be to put the bms in the middle and run the wires out from it like a spider web kind of thing, but you'd still need some kind of loops.
Oooorrrr, you could have each strand go out to it's respective section, then dip down behind the board and then show back up right next to the spot where it dipped. The only difference between each run would be how much wire is "behind" the board that isn't visible. But from the front, you wouldn't be able to see how long the wires were.
Another idea would be to run the wires through a grove made in the board. Then as each wire passes another section, another wire is added and the grove gets a little bit wider and all the wires are ran ribbon style up to the bms.