Looks like a lot of fun! Have you thought of a function generator, instead of Pamela's Workout? Something like "Function", or even "Mod Tools" might give you a bit more by way of modulation. I was always under the impression that Pamela's Workout was akin to a clock generator, not so much mod source -- just my understanding on it, though.
When I started building my rack(s), I based them on systems that were already existing, and I know Perfect Circuit has some small systems like this that might serve as a good template.
Keep it up!