I would agree with you in a market based environment. However, that's not what we have here. In this scenario you only have one player, and that player holds the purse strings and has the airports and airlines bent over a barrel. Airlines and airports are heavily subsidized by the feds. I don't consider a tiny airport in Florida opting out of the TSA as win. They probably received little funding to begin with.
By not questioning the reasonableness of the federal governments search procedures, I think we open ourselves up to the common route of every government, mission creep.
Would it be reasonable for the TSA to collect 4473's and use that as a criteria for "secondary"? We've already seen no fly-no buy, so perhaps this isn't too far fetched.
At the end of the day, if nine lawyers think roadblocks are okay, I would guess that nine lawyers would give an okay to the TSA. Our interpretation of the constitution simply don't matter. It's about nine lawyers that have been churned out of TWO Ivy League schools.
I don't think there's anything reasonable or okay about the TSA. I just don't think the searches are a 4th amendment issue.