TNA on tv comes across as small time and a bunch of nobodies, even if they are talented wrestlers. Christian is much more likely to wind up at TNA than Jericho, and while I like him a lot he isn't a major acquisition for them.
When WCW overtook the WWF they did so with the strength of top WWF stars coming to WCW. They also had a few credible home grown stars (Sting comes to mind). TNA looks like the elephants burial ground of WWE castoffs. Christian or Jericho won't change that impression.
Basically TNA has a long road ahead - they can be a credible 2nd national promotion, but its a long way off. None of their home grown/local talent looks like a star and they have nobody to make them look like stars. The guy I like the most is Samoa Joe, but he looks like a guy working an independent show down at the local Knights of Columbus (even though he isn't).
The thing is it may very well be going back to what you were talking about with the semi-national circuits. WWE isn't pulling in the numbers on USA and it shows. Five-ten years from now will there be a 2 hour wrestling show every Monday night? Contracts nonwithstanding at this rate, probably not