You could always try to, instead of going for the adhoc route of the late model AT STuG, rewind time a bit and go for the models that they were intended for: 'Short ranged' assault gun support.
It would mean slipping a Thumper Cannon into the mount that the AC-10 current fills but it would free up 2 tons for additional armor or ammunition. Plus, you get an indirect fire capability, scattering instead of full-on missing, and an AOE... only 5/2 but considering that the original Scorpion had only an AC-5, this is, in general, an upgrade in capability. On a cheap, lightweight chassis, having something you can target a hex instead of targetting directly and that can be beneficial.
Just an option honestly for a Succession Wars era model (3012 being the introduction of the gun). I came to conclusions very similar to this one a while ago and have come to enjoy using mass, cheap indirect fire from vehicles very similar to this to back up cheap foot infantry.