AFAIK the Voyager has an old school microcontroller with external bus and memory devices - in which case it's easy to reverse engineer for firmware modifications and even adding memory. The MatrixBrute uses a highly integrated microcontroller with an internal bus and memory - not easy to reverse engineer or modify in any way (impossible even if firmware readout is prohibited, a common security feature of such chips). So any extra memory banks are only possible if there's enough room in the flash memory inside the microcontroller chip. Could be, could not be... If there's enough for one or more banks, it would be cool to see that taken advantage of in a firmware update.
The aftertouch is indeed a bit touchy, with the sudden response, and selectable aftertouch curves is a requested feature. I hope that will happen. If not, an after market board could be made that alters the response from the resistive strip that is used (like the one you got for your Voyager). This could potentially be done without the schematics since aftertouch is a pretty simple thing electronics wise.
