So, I’ve got some good news and some, well, good news. 
First, I succeeded in developing an AutoHotKey script that prompts for a track count and steps through a series of channels, exporting them, one by one. And it manages all the exports in the background, so you can multitask with other applications on your computer. Here’s a copy, in case anybody wants to reference it or develop it further: cubase_pro_11_batch_export.zip (2.7 KB)
Second, and more importantly, I’ve since discovered that Cubase 11 Pro can, in fact, perform this same operation natively, and with much greater flexibility.
To batch export a selection of Channel Groups (or Audio Channels, etc.) through your master bus, follow these steps:
- IMPORTANT: Enable Solo Defeat on your Effects Channels and Groups (or your exports will be dry because Cubase solos the target tracks during export, effectively muting your Effects Channels)
- Choose File > Export > Audio Mixdown…
- In the Channel Selection window, choose “Multiple” and select the desired channels to export
- Choose your desired File Location and File Format settings
- IMPORTANT: In the Effects drop-down, choose “+ Master/Groups/Sends (CSPM)” (or your exports won’t be routed through your master bus)
- Export (or Add to Queue and Start Queue Export)
Your exports will be uniformly processed - routed through the master bus, complete with insert effects, volume automation, etc. - ideal for producing stems, etc. and processing stems and alt mixes en masse, as you might in a mastering session.
I hope this is helpful.