My own theory is that Neal's past wasn't a happy one: not necessarily tragic, but he definitely wanted for a lot to the point that he probably swore to himself that he would never suffer that life again.

I can totally get on board with that. I wrote one WC fic and attempted to explore his aversion to guns. It was fun to imagine, but, like you said, it's hard to settle on one idea in case the show actually comes out with their version and you're disappointed. ;)