He got annoyed about the penalties? Woot?
That regiment better be about adding flavor and an interesting background for they seriously get slaughtered if they bring it down to numbers when they engage any kind of a decent foe.
There is a very good reason the IG uses Lasguns (Pretty awsome weapons for our standard) and not bows. And the only reason his regiment might survive is through adapting and utilizing what ever is at their hand. A bow might land a nice shot, but It wont win a serious firefight. So if he wants to deploy a Frag grenade farther than he can throw it by hand he should use a friggin sling or dont do it at all.
The solutions are given, if he is to stubborn to use them and demands some crazy houserules that cater to his very narrow Idea of playstyle, you as a GM should stop at that point. It is not your job to make his ideas work.
Edited by FieserMoep