Your question is a little unclear as to what your actual problem is. You already have gear to make drones, but I assume you are wondering what to get next in order to fully realize your Coil-like fantasies?
In general the answer is: play your system enough so you know it back-to-front, then ask yourself “what exactly do I want to be able to do that I cannot yet do, due to lack of gear functionality?”
The only thing I can see missing is a decent reverb and delay. For the space-conscious, Pico DSP is good.
I would not recommend Cold Mac unless you know exactly what you’re doing with it and why. Like most Mannequins stuff, it’s deliberately obfuscatory and confusing, despite being extremely powerful.