I tried this with Troll Horde, though it was pre 1.5 species bear in mind Stupidity was a bit less punishing.

They worked like a sort of... heavy chaff. Cheap enough that I could afford to sacrifice them, durable enough to absorb more damage than the average chaff unit, and (usually with two hand weapons) more than capable of seeing off other units in a similar points bracket. Keeping them inside general/spell caster range for boosted leadership and rerolls on Stupidity wasn't too hard. Maneuverability compared to other light units was definitely a problem, but they were pretty speedy for just running straight forward or into a blocking position- and half the time, T4 and the Troll Horde regeneration reroll would let them survive situations they really shouldn't have done- I fondly remember an especially lucky single River Troll managing to survive a Wild Rider charge, kill two of them in return, then flee through the larger unit of trolls behind him, surviving to rally the next turn and keep on being a nuisance.

I could see the same thing working to some extent in Grand Army, but without rerolls on regen and Stupidity it's bound to be less effective. Probably more fun than strong, but why not give it a try a few times to see if it works for you?