From a legal position this idea would not get past the WTF thoughs of a judge but I still like the idea.
http://machineslikeus.com/news/why-not-require-all-religions-provide-proof
The idea is not crazy, although going straight to court may not be the right path.
https://www.youtube.com/watch?v=TqL_AA3mank In this video, Dawkins talks about the religious tax exemption.He says you get it simply by declaring yourself "reverent". If all of us declared that and demanded the exemption, it would flood the system and cause a evaluation of it. Before that, Peter Bogohassian talks about his book "A manual for creating atheists" in which he discusses an exemption for people who are delusional. If they declare it is a religious experience, they are exempted. These are antiquated laws that should be changed, and can appeal to moderate believers as well as those who hold stronger views. Just getting a Christian to think about being in the same category as a Scientologists will stir the conversation.