How about an option for whether or not you're broadcasting your own threat? That way people can turn it on when it's important, but otherwise only the tanks would need it.
I would also be in favor of any KTM compatibility being separate from the main addon, if that's possbile. Like, Threat-1.0 and Threat-1.0_KTM or something, if that would be possible.
Threat-1.0 is a library to calculate threat. Whatever you decide to do with that data depends on the addon made to display/convey it.
No, pretty sure Threat-1.0 is managing all the data, including syncing. Violation and Omen are just GUI frontends that display the data.