I went the lazy way myself. I'm making a Eurorack module out of mine with all the analog and digital control inputs wired to pots and switches. For CV control, I bought a doepfer a-192 voltage-to-midi interface module (though discontinued, Analog Haven still has some) which provides 16 CV ins. I will probably mount them both in the same panel. With that setup, although maybe not as elegant as a custom interface made for the Axoloti, you still have no worries of overloading the CV in on the Axoloti and have PLENTY of controls to play with if your patch needs it. I thought of dedicating some of the digital I/O lines into being gate outs with a simple transistor circuit, but that and the front panel (Front Panel Express) would be the only custom parts.