I started a basic design for a Eurorack panel. My design started with breaking off the DIN connectors and stacking them under the main PCB with standoffs. I decided that space wasn't that much of a concern and instead made a full width design with a field of pots below. I removed the 1/4" stereo jacks and replaced them with dual 3.5mm ones. In my design, which was aimed at the least hassle as possible, and the least amount of external custom circuitry as possible, all the analogue lines were to be wired to front panel pots and digital lines were to be wired to jacks. For CV control, I opted for using a Doepfer CV to MIDI CC module that would give me 16 CV inputs on top of the 16 knobs. This module would sit next to the Axo modules and be wires internally. I also considered one panel and mounting the Doepfer module and the Axo in the same panel and only offer one set of MIDI DIN jacks to the outside, but decided that separate modules would be more flexible (that way the CV>MIDI module could control my Nords if I wanted to). Analogue Haven still sells the discontinued doepfer A-192 voltage-to-midi interface and I got one of those. There are other alternatives available.The only custom electronics needed might be level conversion to and from the Eurorack audio and to Eurorack gate levels (a simple $5 pub from SparkFun can do this). I designed panels on FrontPanel Express (just have to do the graphics) and just have to get the time to put it together. The CV to MIDI converter module makes all of it easy and the cost, for me, is worth it for safety and convenience reasons.