This is basically a "master issue" / feature request for anything related to keybinds (that I could think of for the time being).
This currently includes:

• Support for Modifier keys
• Advanced keybind conflicts / "contexts"
• Possibly interchangeability / compat with forge's system
  (as well as any established Fabric standards, if they exist)

Going to mark this as "missing api" for now, as Dan already said we likely will not be implementing this unless a standard emerges within Fabric API itself, as there is currently simply too much fragmentation and compatibility issues with what exists on the market (and yet another dependency for mods depending on Arch doesn't exactly sound like too rosy of a prospect either :P)

AFAIK, the established Fabric standard for this is Amecs API.

Amecs is not an established API, it suffers from immense compatibility issues and is not widely used / adapted. There are no plans to supporting this in architectury api, you can ExpectPlatform this to make this on forge, with your own choice of library on fabric.