Mixer to tame a hot amp loop?

[Manc]

To cut short a long story - I spent the last two months fixing my old Yamaha T100.
Turned out it was a bust octocoupler. Since I was at it, I also recapped it and did the infamous "choke mod".
This brought it further in Soldano-land, however its biggest weakness remained un-touched, specially now that I got into pedal-making.
The loop is waaaay too hot for pedals to handle - so it will work on the clean channel but once you switch to the crunch it doesn't sound exactly great...
I understand this is a common issue with the glorious SLO too, so at least these two amps have some similarities 😂
I don't want to fiddle with the amp, I mean - I brought it back from the land of the dead and that was already a big ask form my abilities.
My question is - can I make an external unit that will live on my board and that can tame the signal from the loop? Something that is also able to restore some signal back into the return?
I looked up the units Ceriatone makes (dumbulator sort of thing) but apart from a layout I could not find any schematics