I should also mention - please don't take offense - that the word was that the Cardinals did look at this idea when they came up with the new logo and uniforms, but rejected it for obvious reasons.
With the Ravens, the original "shield" logo was something that a fan (I think he was a security guard at the Ravens' HQ or something like that) submitted and the Ravens ran with it. When he asked for compinsation, they balked and the whole thing went to court.
Instead of paying the guy, they ditched the logo and came up with the current logo as a replacement.
NFL teams (or any other team in the four major sports for that matter), won't even so much as glance at an unsolicited design. NFL Properties handles all of that stuff.