the best use is if you have to march them, you can adjust their ranks to shoot more . If you are losing your shooting phase you can at least redress. Another is a detachment of handgunners or crossbowmen changing ino a 5x2 from a 10x1 for a supporting charge - if you judge it being more effective than supporting stand and fire.
It's extremely niche and absolutely not worth it, but it's the only case i can see. Both missile units have it bad when they move so they should not be moving at all. That is unless you can freely redress them if they stand still, in that case ot could be useful for having more models shooting after starting with a smaller rank.