Having decided to go DCC to simply the wiring and switching in the yard, a review of all of my loco stock reveals that this decision is a reasonable direction as all of my freight locos (GP-35, SD70, etc.) are readily upgrade-able to DCC with drop-in decoders. But alas, my passenger locos (F7, Mikado, etc.) are not upgrade-able to DCC! That realized leads me to adjust my DCC decision as follows.
Recall that the Central End has two basic scenes: a freight yard and a passenger station. Since my intention is to run all of my passenger trains on the outside mainline that runs through the passenger station scene, I've decided that I must retain full DC operation for the passenger station tracks. Thus, I now intend on blocking the separate station tracks and installing the electrical switching and mainline power control as originally planned. Even with this solution installed, the outside mainline through this module will still be DCC-compatible by simply putting all of the electrical switches in the powered on position.
For the last couple of years, we've been using my MRC ControlMaster 20 Power Center units for running the modular layout at shows. I use these at home as well. My modified split DCC/DC arrangement will likely be configured with having one CM20 power the outside mainline and hook the inside mainline to the DCC system. The CM20 has a 16 VAC output that could be useful to power the DCC side but I suspect that it lacks the amperage needed since it is intended only for AC-powered accessories - I'm guessing that it only has up to 1.25 A which is clearly inadequate based on the systems that I've been looking at so far.
Meanwhile, I've looked at the loco decoder options for Z-scale and it appears that I've got two primary decoder vendor choices: Digitrax and Train Control Systems (TCS), both of which offer drop-in decoders for my particular locos. With the lack of clear consensus out there in the train forums, I'm leaning toward getting two of each to updated my existing Geeps and after some time playing with each, I'll make a decision as to which to go with for my remaining locos.