My linkshell and I talked a bit about that last night. Going FTP would probably be the death of FFXIV. Bots and gold farmers would pack the servers. SE already moves as slow as a glacier to take care of the ones already under PTP. The situation would become far far worse as FTP. Which leads to all servers eventually being as packed as Balmung is, so hello connectivity issues around all the servers especially on patch days. I could see it taking the FTP model SWTOR has where you're limited to what you can do or have access to unless you become a subscriber or spend money for unlock tokens per week.
On top of things you mentioned, the major FTP games offering far far far more then FFXIV has to offer. In terms of content, new events every now and then in game, customization and so on. FFXIV is second to WoW and that's mainly due to its the only two major games really left that use a sub model. What does FFXIV offer in the long run that isn't offered in other FTP games? I honestly can't think of one thing at all that makes me wanna scream about it being worth it. Well okay maybe G-pose, but that's all I can think of.
That and I shudder to think how SE would handle lock boxes/RNG boxes >_>