I'm one of a whole bunch of reviewers for Black Hat USA, which is the largest vulnerability research conference in the industry. For the past several years, if you were to submit a universal WAF bypass talk, enabling you to evade detection by every WAF on the market for every common attack, there is a really good chance that talk would not be accepted --- too boring. Almost certainly a WAF bypass that evaded all detection by a single WAF vendor wouldn't make the cut.

So, no, not really interested in generic SQL detection rules in WAFs.