Very true, but would the amount lost from regular subscribers like me, who'd pay a little be made up by the people who would spend a @#%^ ton?
I don't think so, but who knows? I'm not saying it's a definite, just saying it's a risk I doubt SE would take.
And again also it would depend on how well it was implemented. I make no suggestions on how a good f2p be done on a game like FFXI.