@gardners I've forked the project and started working on a DOS wedge:
https://github.com/FeralChild64/open-roms/commits/master
If I'm doing something really ugly, please tell me. I didn't touch 6510 assembler since my childhood. Plan: use it as a simple testing tool to fill-in gaps in the current Kernal IEC support.
One question: are you planning any kind of compile-time configuration? Like: FEATURE_DOS_WEDGE=Y somewhere... I try to optimize code for size, but we might run out of ROM space at some point.