I am neutral to the idea.

I would continue paying my normal monthly fee, and would probably not buy these "subscription items" from SE - nor another player for that matter..

But I do know of a couple of people that do have a bit of real life financial struggle (who in my opinion should be focusing on real life, but i'm not one to judge), that would use this system and I can see it working.

The only way this sort of thing would effect the market would be pumping more gil into the world (by NPC'ing items etc). It would simply be like SE adding an expensive / hard to obtain item (such as say, a double melded class weapon or something)~ There is no impact on the economy as gil is not added/taken out of the circulation.

As for those willing to pay for other people's subscription in real life $$, let them. I personally wouldn't pay real life money for in game gil, over and above the monthly fee - but I can't see it as being an advantage over anyone else. You could just as easily open up a 2nd account (ie paying double subscription) and use some kind of farming/gathering/crafting bot to make that gil... This just takes the silly "third party program" side out of it and uses other people's time.

tldr version: It's a good idea, even though I wouldn't use it.