If you think there can be a metric to determine an expected value for an average blogger on Steem as a baseline then let me know.

There's no way to really know this without looking and trying out a few to see what is statistically significant. I would be pretty interested to find it. You could also throw some neural net magic at it with as many metrics as you can thing of and see what comes back as a predictor.

So a first step would be to get as many people / companies as you can that are already here to supply the information that is not on the blockchain, as you said "how much specialized knowledge they have, who they know, how attractive they are physically or by charisma, what talents they have..." and supplement this with an independent "fuzzy" analysis of their general persona.