That was my problem too, and it's why I eventually dropped the idea. Check out my comment here: https://news.ycombinator.com/item?id=18643591
I'm not sure if crowdsourced data would work, and I think this probably needs a team of researchers and immigration experts to give people enough confidence (especially if they're going to be paying for something.) Or at least a license to use the Timatic data. I went down this road a while ago and realized that I would probably become either a Timatic competitor, or a visa agency like https://www.visahq.com