What is still missing for me is something like a headphone out to listen to the direct out of the rack. Because what is the use to mix your stereo drum singnal within the Rack if you're doing additional mixing listening outside of the box anyway. Also I'm not really sure if you really need the symmetric input of your drummachine singal you mentioned earlier? And wouldn't it will be line signal anyway? wWth lots of cheap adapters you do not get the performance you would expect from symmertric xlr cable.
I'm also just starting out but even looking at the updated rig I feel like there are a lot of complex boxes with just little facilitation? So maybe you could mix a line singal of your rack and then mix outside of the box with the drums. But thats just my 2 cents.
FYI, there are maths alternatives like combining multiple "Make Noise Functions" or "Befaco Rampage", but you would not get as much functions with the rampage as it is missing the two additional attenuverted channels. So you will always end up loosing more rack space with the Rampage in a system.
cheers
alex
The Machine: https://www.modulargrid.net/e/racks/view/1601144