Sounds like the E-MU Proteus is just a wavetable synthesizer anyway, just with ROM samples. Hardly any different from hooking a separate device (MT-32 or the like) into a MIDI adapter.
Not sure I understand your sentiment here. You could also easily
say something is "just" a sampler, or "just" an analog synth, or
"just" an FM synthesizer. What type of ground-breaking Zorro
synthesis board should one expect?