I recently got my modified keybind working, although I have an issue, addons are a bit wacky and have different keybinds for things since orbiter isn't built for WASD, is there a way to change the keybinds on vessels?
The keys for addon-specific functions are usually hardcoded. It's up to each addon to provide a way to reconfigure, but as far as I'm aware that's not common, don't recall ever seeing it done at least.
Feels like there's an unwritten standard to stick to certain keys, or maybe it's just subconscious influence, and WASD are generally not used much. But it depends on the addon and how many extra keys they need, there's no rule.
Usually the way devs (or at least me) do it is to look at what keys are used by Orbiter by default and stay away from them.
Anything else is fair game. And yes, vessel's keys are hardcoded in C++.