How about using it as a Space Marine Centurion? Those buggers are bigger than terminators.
Thing is, even though this particular robot model is taller than a terminator, it is also rather spindly, and does not have a (modern) terminator's mass.
Maybe some of the other models do though; the Castellan is decidedly bulkier. Probably the largest of the old robots. The Cataphract is bulky but too stunty, and the Colossus and the other one (always forget that name) are again too thin in the limb.
Certainly none of the old robots have the mass to fill in for those ridiculously bulky Centurions. But then again; proxying gives one more than enough room for interpretation and improvisation (anyone still remember Mr. Carnifex?
)