Nono, this project is still NOT stuck! Just the pace is a little down.
To achieve the next milestone (which is an expansion port), I need to switch to another FPGA Board with more I/Os. I already have one here, but as I always tend to overread specs, I missed that there is no SRAM, but only an SDRAM on this Board.
And no, I'm really not in the mood to write an SD-Interface. So I've ordered some SRAM-ICs which I will hook up later.
In the meantime, I was able to programm and read the Flash IC (CIF) on the Board. So all Roms (Kernal, Basic, Charset) are no longer occupying valuable BlockRam.
If everything goes well, I will have an expansion port up and running still on 2012 :-D