Buy large plastic flies from a children's toy store of some sort and throw Plaguebearers on?
Perhaps go 1x 20 DSing in and 2x 10 with icons, so the reinforcements can get called in where they're needed.
But yikes, an Infantry melee army that can't run. Reminds me of 4th Ed *shudders*
What sphinx of plascrete and adamantium bashed open their skulls and ate up their brains and imagination? Imperator! Imperator!