I suggest another Core: The KIM-1
A Clone using a 6502 CPU, two 6532 RIOTs, the two ROMs, 64kb RAM and some glue. Maybe a silversurfer driver for serial output and the audio jack as tape I/O
What do you think? I'd offer a 100,-€ reward for a working core 🎁
Schematics of a Kim Clone called Pal-1 using 6532 http://pal.aibs.ws/assets/schematic.pdf
6532 in VHDL https://opencores.org/projects/vhdl_6532_riot
nils