I think you just have to break it down into classes.
Top professionals. At any national or large regional they have a shot at making top 5 and placing in the money. These players seem to do this often.
Professional-Players who make brackets at nationals and large regionals will place after top pros. The reason I call these players professional is because they are typically the tops of their regions next to the top professionals. In any case, by definition I would expect them to be the ones claiming the money at locals and smaller regionals. So making money=technically professional.
Semi-professional. These are players that often place top 3-4 and get money at their locals. At a regional tourney they compete for the money and top 5 placings.
I also agree that the top 3-4 players of a character are considered professional examples of that character.
Top pros-m2k, armada, hbox, mango, jman,
professionals-shroomed, taj, eggz, axe, silentwolf, zhu, SS
semi-pro-the dudes who **** everyone else
acknowledged-players who are known but may not travel or take the game as seriously. Considered "good"
scrubs-local(semi) pros have at least seen them b4. have the basics down and are working to improve
randoms-they just ****ing show up and pay money. they dont have the basics down