If you want this all to have a certain rhythmic undercurrent, Pam's is probably the way to go. Also, a Toppobrillo Sport Modulator seems like it'd be a good calls for a noise/ambient case like this as well - lots of opportunities for going from modulation to audio rate oscillation and everywhere in between. I think it would fit this setup particularly well for how it can be both a self-contained drone synth in its own right as well as a toolbox for your modular setup.

An attenuverter or VCA would also be helpful here to give the textures even more movement and fill more space.