So far they're only talking about fees for bizjets, but of course that can change at any time. Once they get the user fee concept established, it will expand and grow. Nobody knows yet what would be considered use of ATC services; so far it's just somebody's idea of what oughta be done. Details TBD. But here the devil isn't just in the details, it's in the basic concept itself.
How many non commercial pilots actually use ATC? Huh? Lots! I fly into airports with control towers all the time. I often call for radar service around big airports and sometimes flight following enroute. I fly IFR very rarely, but many noncommercial pilots file IFR everywhere they go. I live near a huge complex of restricted areas that seem to open/close on a whim, and I often call Center to check their current status. Every one of those things is a service looking for a fee if the user fee system gets adopted. And safety would definitely be impaired, because fewer of us would file IFR, use radar service, or call ATC for necessary information.
Your point about outlying airports is interesting--you're right, outlying airports might see a big increase in business. But I'll bet the FBOs at those airports aren't supporting user fees any more than the rest of us.