Probably puting softsaturator as the first and the last insert plugin on a buss or a channel.Curious: what's the "summing trick"?
In old days, one could do that with saturator in VstDynamics of Cubase even.
The first one could mimic behaviour of mixdesk input stage, the last one would stand for post-eq buffer stage nonlinearities. (etc).
It would be interesting to see if some experimenting developer could make a plugin that would mimic nonlin behaviour of an opamp with class-a pulldown -resistor- (not the "perfect" one, with a constant-current source). I found such modded stages adding more fat to the sound.
