After additional iterations, I took the initial advice of using an external drum machine. Therefore, I removed the Blck_Noir and Erica Synth Drum Sampler. I will own Blck_Noir day, but it will unfortunately not included in my first modular system build. I also kept the TipTop effects in the case to prevent or limit the use of an external effect units and pedals. Below are the new modifications:
I plan to run the WMD Performance Mixer's main output to the stereo external inputs of either the Native Instruments Maschine+, Pioneer DJ SP-16, Roland MC-707, or Roland TR-8S. Since I already own all four, at least one of them can provide the drums and, if needed, additional sounds.
The overall setup should be rather compact unlike my present studio setup with multiple individual synths.
Thanks for the help!