Why not writing this in a "modern" env? Say Qt? Don't get me wrong.. I'm an old geek who enjoys retro tools and own a couple of commodore and Z80s. Just asking for your rationale while playing with the idea of writing the same using a game engine.
I'm also part of the FreeDOS Project, so part of my goal was to write this in DOS too. And C was the easiest path for me to do that. :-)