I tried it on a 6128, I could copy and run as expected. I liked the cpax command. Great job Ast. Now I'll look for that file manager tool that people did for your ROM and Acmedos.
I tested iMPdos on a classic 464 and the greys keys version (edge as well), x-mem detected but small bugs on screen after ùx, crash and reset when trying to load from the x-mem, and I had to use uppers letters because many keys (without SHIFT) are weird, exemple: e = enter, space = D... I cleaned the edges on the PCB, I'll try again tonight, but I think it could be something else. There's ROM 0 and 7 and imPdos between. (I only installed your ROM on 3th slot)