You can see the coating on the stuff I have; salt water fishing leaders.  I have never bothered removing it and have had no problem.  However, I either wrap or crimp, no hi-tech swaging.   

My #7 Easy which I built in either 2001 or 2002 finally met its demise after, I am sure, well over 1000 flights.  The outside wing blew off.  I salvaged the useful parts.  The bellcrank is 4-inch white plastic (Sig?) The leadouts are coated leader cables.  The leadouts have the Teflon tubing for CyA glue (large size from Hotstuff), rather than metal tubing,  as bushing in the bellcrank holes.  There is no sign of wear on the bellcrank, the Teflon tubing,  or the leadouts.  So I would say the Teflon tubing works fine as bushing on plastic bellcranks. 

I recall seeing Don McClave's  PT-19 Stunter bite the asphalt at Clover Park in Tacoma, when his bellcrank sawed through "green nylon coated aircraft cable".  Actually, I'm not sure this stuff is made for aircraft, but it is certainly used for tethering tooling pins and doodads to jigs and fixtures for a large local aircraft corporation. I don't remember what sort of bellcrank it was. Maybe one of the Fireballs would remember or could call Don and ask?

Jim T's experience is interesting, with the teflon tubing bushing. FWIW, Sig 4" BC's are black...those self-neutralizing jobbies. Very sturdy, thick and kinda heavy.  All the coated cable I've seen (fishing leader and tooling tethers or lanyards) are very obviously coated, and they are not likely to be coated with Teflon, but Nylon of some sort (about 60 varieties of Nylon).

Personally, I'd use bare cable. I think the friction would be less, and any damage easier to look for.  Steve