Like I need another big project :-)
The IBM Datamaster is an interesting system, but it was doomed. It had an 8-bit Intel 8085 processor, cost $9000, and came out in July 1981. The IBM PC had a 16-bit 8088 processor, cost $1565, and came out a month later. So there was no reason to buy a Datamaster
There's a good description of Datamaster in "A Personal History of the IBM PC" by Dave Bradley (one of the PC's designers). Unfortunately, it's paywalled.[1]
That sounds like a great starting point. There's a university library 500 meters from where I work, so bypassing the paywall ought to be easy.
And thank you for all of your articles over the years. They border so close to applied physics they are fascinating reads.