I fear I might be going down the rabbit hole of re-implementing the entire in-game interface.
On a serious note: even having the ability to create/change binds on the website and save to the "bind-file format" would be great! It would still be easier than using the in-game interface, (Imho).
Oh you will be going down the rabbit hole for sure. Detecting joysticks, gamepads, wheels, pedals, hotases and whatnot in javascript? FUUUN. Validating user input? Even more FUUUN. Conforming to an XSD sheet (bind file format as you call it?) which we don't have to make sure game understands it and doesn't reject it outright? FUN FUN FUN. Not to mention the simple mundane work of all form UI controls, which even when using a framework can be a PITA. Roooight
All that "FUN" may be spent on implementing some useful stuff mentioned earlier ;-) So yes, in theory it sounds like a good idea, but effort to gain ratio is abysmal, considering you already have the in game UI that does the job just fine. If you really despise the interface so much Grendell ;-) you can open the file with a text editor (Notepad++) and try to understand it - you will be able to do adjustments, it's an XML readable in English ;-)