I'm not going to give specific advice, but advice if I suddenly acquired your system and the things I would check.
My first consideration would be able to stop, start, and reset both the Nerdseq and the Erica Drum sequencer together. If I start playing one sequencer from the beginning, I should be able to slave the other. This might be done through MIDI or CV through clock and reset. I would look through both for Clock-In, Clock-Out, Reset-In, Reset-Out features.
My second consideration would be a mixing. I'd just go Full-Monty and get the beast that Befaco makes. The Techno-System comes with a lot of sub-mixers. But I'd like to be able to take everything to one main performance mixer. Depending on what modules you get for the Befaco mixing system, you might not need the Intellijel VCA.
Third, utilities. How are you doing on sample&hold, logic modules, slew limiters, etc.
Finally, modules like Plaits would be a great addition as they don't need a lot of support... just a gate and pitch CV. I'm assuming that the main focus is the Techno System and your other modules will support it. Add in a nice reverb and I think you're near golden.