Wow! Ian this is awesome! I messed around with Bero's port back in the day, but didn't spend too much time with it. I think I remember it to be lacking some things.
I absolutely LOVED Hexen as a kid. It was actually the first FPS game I ever played on my uncle's PC. I know it's a flawed game in many ways, but it was really ambitious at the time and a lot of fun. I even ended up picking up the N64 version, which had co-op multiplayer which was a blast.
I would love to see more work on this and more features added. I'd definitely sit down and play some Hexen again on my DC.