Thank you warlock016, good to hear that you could make good use of the quarantine time! My Filter building knowledge is limited to solder different kinds of capacitors in electric guitars, but thats it. I will keep my eyes peeled for a new kit.

For starters I'm going to build my own short bus / gate combiner, I found the schematics on the doepfer A-100 DIY page http://www.doepfer.de/DIY/a100_diy.htm and found additional input in a muffwiggler thread. While writing this post I remembered that might still have some parts from a baby 10 sequencer I (failed to) build back in 2013! So now I even have something to measure the fitting for a 5hp version:
diy module

Now I'm checking parts. I really want to get some of the sexy befaco bananuts for any DIY kit thats coming, and I even found a seller here that has black and red in stock! Getting only a few diodes will be annoying tho, so I'll check if I can get myself a good kit of basic resistors caps and diodes again.

@Kel_, Thank you for poiting me to the Krell Patch. It's really a fun exercise to create solutions to these kind of challenges for me. The entropy is a tempting offer, but exploding shed has the kit in stock and I want to order the jacks trough them anyway so I can also save a little bit on shipping.

Coming back to @GarfieldModular I have two of the Teenage Engineering Pocket Operators but don't intent do solder them in the rack. I read a bit about it but they don't sound nice enough to waste 12hp. It's still fun to trigger the respective clock in via the cue out on the headphone jack. Right now I'm also using the Teenage Engineering OP-Z to control the rack via midi, but need to setup a computer in between, as it doesn't come with native midi but only with an extension card.

More sonic explorations with the Rack here: