Ok, the time has come to start releasing some files :-)
This link contains everything needed to build a simple Base18 system with RAM and SD card, and program it with the firmware as it is on 31 October 2019.
Of course, the hardware is still pretty much in alpha stage, some things may work, some may not. I am still testing and will be providing updates in due time. The firmware is almost at "release" stage and I will release the sources once there is enough third-party evidence that the system actually works elsewhere away from my desk.
In the final hours I decided to through in a simple PIC18 disassembler built into the system monitor. That went quite well, but unfortunately on the expense of a few KB from the IFS: drive. So, IFS: is down to the absolute possible minimum now, but at least still there.
My plan for finalising the development of the firmware includes some sort of absolute bare bone scripting automation so files can be started automatically on power on, or from other files. Maybe a few extra entries in the BIOS function table as well.
That's for now...