Number 2 is okay. The other ones come off as passive or overtly aggressive. If a potential vendor tried any of those, I would politely thank them and find someone else.
I work for the state so it's easy for me to say "I can't work on that because it conflicts with my work ethic responsibilities. I'm not allowed to take paying jobs which connect to state system roads because it's a potential conflict of interest." (But what if you do it for free?... "do what now?")
Favourite word I know. And everyone understands it.
Favourite word I know. And everyone doesn't really understand it.