I have committed heresy or a sacrilege on my Long Branch boots. I pretty much only wear boots and I was getting pretty frustrated from having to hurriedly remove my boots at the TSA line when travelling. I didn't want to wear shoes and I considered Chelsea boots but couldn't quite get into them. So I arrived at side-zip boots. But none of the brands I like and/or am knowledgeable about have side-zip boots.
I considered some nicer Italian boots (Marsell, Buttero, MMM, etc.) but then thought about having zips installed on one of my existing boots. I contacted Nick at B. Nelson but he declined to undertake the project. He was concerned about the heel counters getting in the way. I respect his expertise and opinion but I am stubborn and thought I'd try a local cobber, who had no such compunctions about tearing into my boots.
$40 later and maybe not a perfect job but I think I may have solved my problem. How they'll hold up with wear remains to be seen. But I am excited at trying them out. I don't think I'd do this to one of my nicer boots but the LBs are great beater boots for travelling.
Also, applying for pre-check could make your life a little easier.
Nevertheless, good on you for being game to try something unorthodox!