I like your theory. This tangled family tree would be Rumple/Gold’s ultimate insurance if Neal is Bae. The way you lay it out makes a really convincing case. I’m really having to keep an open mind about who Neal is. Bae is the obvious choice the writers would want us to think.
the only thing I can infer from Neal for sure is that he had definitely encountered magic before. That opens a door for him being from any of the magical lands/worlds, but these writers have tricked me one too many times for me to side on a definite answer so far.
Bae is a good guess.
I Don’t see him being Peter Pan like some people are suggesting, but it’s just as likely as Bae at this point.
An idea i’m playing with is that Neal is the WIZARD from the Wizard of Oz. The Wizard is originally from the real world and travels to Oz by ballon, eventually returning to his home world. Maybe the Wizard would be older, but they made Hook a young hunk, so why not the Wizard.