I found this site with some pictures and info that might help:
https://shampoch.com/cornerstone-bull-gladio.htmlThe IC in the power section could be a charge pump to get bipolar power. That could make sense given the 2 regulators, but they might need one regulator for the microcontroller.
I notice some blue boxes under the jacks. Seems likely to be relay switching. I would agree Q4-6 look like they are probably involved in switching, maybe controlling the relays.
From the manual snippets, it looks like opamp saturation is used for the side of the board with the slide switch, with the switch adding clipping. I would bet Q1 and Q2 are part of that along with the bat41? diodes. The right side of the board looks like those 6 diodes are used for clipping, with the comp switch choosing how many of them.
Overall, it doesn't look like anything too exotic as far as the overdrive, but I must say I appreciate the effort put into the rest of it.