I would think that the power amp section of the Sunn would not lend itself to making it sound like another amp, being an ultralinear amp. But why would you want to make it sound like another amp? Other amps already sound like other amps.
One thing you might think about, though, is converting the ultralinear power section to a triode power section. That would, of course, greatly reduce the power output, but low power amps are popular these days. It might sound really good when driven into distortion, and should be easily reversible.