Just a little status update:
With CP/M working as a proof-of-concept, an important personal milestone has been reached.
While doing so, a lot of new interesting ideas came up. That's why I am now spending a little time incorporating all the development so far into a VTech Genius LEADER Development Kit - the VGLDK.
Even though I would very much appreciate it, if the VGL support for the Z88DK would improve, I feel like it is a little bit too over-engineered and complicated for the rather "simple things" I try to accomplish. Those being: Enabling everyone to develop software for the system quickly and hassle free.
So I created a Github repo at https://github.com/hotkeymuc/vgldk and started filling it with some initial content. My current focus lies on smooth portability between the 1000, 2000 and 4000 series. (Series 3000, 5000, 6000, 7000 and 8000 may follow eventually.) Additionally, the build process must allow compiling programs for use in a cartridge ROM, as system replacement ROMs, and also for runtime-linking (e.g. when using CP/M or some sort of DOS). I might also migrate the VGL CP/M project right into the VGLDK.