I want to say that it's safe to assume that the gil seller rise has been due to a few factors:

1) Content selling, IE Merc wins
2) Housing

Assumption: Most people who buy primal wins are probably buying gil.

I think that if a person is repeatedly buying primal wins, lets say hypothetically speaking all 8 weapons. There is a very very low chance that anyone can make 1mil gil a week, I highly doubt this is possible. (unless you sell wins yourself lol) **On Balmung, the price for wins can run from 750k to 1.5 million.

So what I propose is this: either SE themselves form a team per server to "sell" primal wins. (actually complete the whole process). Then gather lists of names of people that purchase the content. (repeated buyers should be on a high-alert list)

This list of content buyers could be a good starting point for checking for shady gil activities. I think that anyone that has bought more than their first win should be checked for potential transactions with RMT.