People try to model what the game does but without actually reimplementing all of SC2 perfectly, you'll still have bugs.
I think, on the other hand, if you had a video taken with the production tab open, and did some really simple image processing to determine what is being built at any given time, you could do a lot better than everyone else.
(I've been kicking this idea around for a while but never got past playing around with a single .PNG, and it looks like you have all the hard .sc2replay -> video stuff worked out already!)