I've always thought that a team of 8 people at SE could quell the amount of RMT spam tremendously by having these 8 individuals dedicate at least one 8 hour work shift a week, one hour per server, logged in as regular player characters. The RMT would not know that these are SE employees and would send their RMT spam per usual. This would give these individuals the ability to immediately ban the RMT violating the ToS by simply offering to sell gil, and not only would these individuals be able to ban the RMT who are sending the /tells but they would also see any /say or /shout RMT advertisements.
Why only 8 people? To my knowledge there are 64 different worlds so 8 people could observe 8 servers each, for one hour per server, and they will have been able to observe activity on each world within an 8 hour workday. Sounds simple enough, if you ask me.
My ultimate suggestion/plea is for Yoshi P himself to log on and attempt to enjoy playing the game on worlds heavily affected by RMT spam. By the time he's ready to pull his hair out due to the annoyance of all the RMT spam maybe then we could see some
real action taken against RMT.
However, in my honest opinion, we will most likely never see any more action taken against RMT other than what SE and their Special Task Force are currently doing. As has been stated before, the STF are banning RMT by the thousands rather frequently, so I feel that they will continue to stick with their current methods rather than taking any further, or new, actions to combat RMT.
Edit:
I started a thread about the RMT plague on 3.25.2015 and this is the image I posted:
That was about 10 minutes of hanging out in Limsa.
A year later and the RMT spam hasn't gotten any better.....if that doesn't speak volumes then I don't know what else there is to say.