I've been studying the shit outta that installer. I just found out it does a bunch of tests to determine system capabilities and stores them in a bitfield, such as "is a particular model", "has an MPU-401 interface", "has a Sound Blaster", "has a MediaVision", and "current drive is a CD-ROM"... which considering that's the only place it does such a check iss probably how it knows to offer copying files to HDD instead of only saving RESOURCE.CFG. Not sure how it tells if it's running from a diskette though, but I'd just check if the current drive is < 2 (that'd be C:) and assume A: and B: are always diskette drives.
Kinda feel like writing a custom windowing toolkit with proper control objects, and porting my custom installer to it. Get some proper buttons in it instead of "press Y/N" prompts so you can use the mouse... Besides the main menu not being a list anymore, it'd look pretty much the same.