Here's an idea: take out the SSF noise source and replace it with a Ladik A-530 dual line input preamp. Then remove the 2hp sample and hold and replace it with a Zlob Entropy, which gives you a S&H circuit plus three noise colors in just 2 hp. Nails it! You definitely want an output module; the signal levels coming out of the modular need to be stepped down to line level from the higher levels in the synth itself. Plus that Ladik output has the plus feature of MOAR BLINKKY LITEZ!!!
As for the power starvation...no, don't do that. The idea behind it is that the lower voltage level (such as from a worn-out battery) will result in some interesting sound characteristics, and while that works well with more robust circuitry like stompboxes (especially fuzz, overdrive and the like), my concern would be that the more twiddly circuitry of a typical Eurorack module might not be too happy with the lowered voltages, and the results could potentially be tragic. Some modules, obviously, would be a good candidate for this, but pretty much nothing in my version of the build would fall into that category. In fact, even in your version, only the Optodist comes to mind as something that the ADDAC 300 would play nice with.
Basically, if the power specs say +12 and -12, make sure you're feeding those voltages to your modules. They (and you) will be happier in the long run if you give them what they want.