The concept for such solution is good – based on historical battles – at least I think so…
In the very beginning of Soviets counter attack soldiers on a battlefield were dying not in hundreds, but in thousands and more…
I think that ability to equip already trained soldiers with additional weapons is good, but only if necessary research in armory would be done, and such equipment should costs some resources. This new ability / possibility (in my opinion off course) should be activated not in armory, but in Mustering Tent. But as I’ve mentioned above – only after necessary research in Armory has been done.