It could be done, but your resolution would be hard to deal with on that small a diameter.
I have three distributor machines, all of which use a degree wheel of 8" or greater diameter. Just like cam degreeing, the larger the degree wheel, the greater the distance between degree marks, and the greater the resolution of you results. An 8" wheel would have the degree marks .070" apart...but that is didtributor degrees...which is two crank degrees. So each crankshaft degree is .035". Also, you need an accurate way to measure rpm, which is one half the engine rpm.
The other thing a distributor machine does that would be difficult to emulate in a home brew solution...is the ability to watch all six or eight sparks at the same time, to make sure they fire equadistant from each other. Worn point cam lobes or improperly machined reluctor cores are not uncommon, and the spark can vary from cyl to cyl in this scenario.
That said, it wouldn't be that hard to build your own machine that works decent. But I think it would be just about the same cost and time, to simply try to find an old one yourself...I've never paid more than $100 for one, and was given my nicest one for free. A 1945 Allen synchrograph
It works great and I use it all the time.
Gearhead