Looks like all PSA flights to TYS go via CLT. Only non-stops to TYS are on Expressjet. Expressjet would be great if you get ATL base and a reasonably quick upgrade, but seemingly this is not the case. Driving is OK only of you have to do it once in a while or you have a long call. Don't forget to look into commuting policy, medical benefits and travel and hotels if provided.

Alternatively, you could go to Expressjet for a year, get the jet time and try to get on with a home-basing 135 outfit like Xojet to start your Age 65 transition plan a bit earlier!