if they were longer i'm guess they would have to 're-calibrate' the discharger.
as when it gives you IR reading, it ahs to take into consideration the resistance of the wires etc.
i think the wires are fine as they are....
i have one suggestion though, why not make it 4 cell to? i know 12th is a big thing in the US and there is a huge market for things like this over there...i think you would get even more interest from the 12th scale guys if it was compatible with 4 cells.