The solution is simple:

1.) Recognize that RMT is going to happen. There's not an MMO out there where it doesn't happen.

2.) Recognize that supply here is driven by demand. As long as the demand for gil from RMT exists, there will be others who will supply it, regardless of ToS in a given game. Banning the bots doesn't work, because they'll just create new accounts. Banning the cards doesn't work, b/c they'll just buy prepaids elsewhere. Further, I suspect they're probably behind the DDOS that always seems to happen right after a ban wave.

3.) If the demand is going to exist for buying gil...and it's not going away, the solution is for SE to either to either (a) sell it themselves (which would kill demand but worsen inflation) or (b) to create an official method of transfer between players (which would also kill demand without necessarily worsening inflation more than we already face). This is exactly what Blizzard did with the WoW token, and not only does it work...it gives Blizzard extra money (the buyer pays $20 for an amount of gold, the seller collects $15 worth of gametime for that same amount of gold, Blizzard profits $5 every time).

TL;DR: all the problems go away once SE decides to create their own marketplace and effectively drive the bots out of town.