I'm gonna go against the grain a bit and say it might be worth a try. I wouldn't bother with dealer installed options like tonneau covers though, those are constraints. The other options you listed aren't constraints and the bed rail and spray liner are currently discounted.
Here's a 1 minute...
Bold. Faced. Lie.
Again basically another lie. Ford or any other manufacturer for that matter wants their dealers to follow the instructions given. It may not be a hard-and-fast rule but Fords intentions on what it expects dealers to do when it comes to price protection is spelled out clear as...