Dunno what the ordnance and ammo would weigh... Maybe there's enough power margin to add standoff applique armor on the (nicely sloped btw) front, slat on the sides and light ERA on the roof. Add one or more MG OHWS or an Israeli-style glass turret if there's room, and you should have a decent urban support vehicle.
That is, provided you are stuck with a SU-105 of an M-113.
Otherwise you'd probably be better off with a turreted AMOS-style high-ROF gun-mortar, heavily uparmored, on a decently protected chassis (think BTR-T, BMP-T, Namer, Temsah...)
That's for the urban support, now by the look of it this one could also have had some interest as highly mobile SPH in armored units, back in the 70s.
Mark, do you know when the idea dates back to?