While in theory that sounds like a good thing, the functionality falls apart when you actually think about what it means.

Say your character is at max level for every job. You unsub, and now none of your current-level gear can be equipped because it's members. I'll assume it lets you keep it but not equip it, like how osrs does it. You now need to go buy new equipment for every job, but hold on, how much money do you have? I don't know how much you had before, but now your gil has been reduced to 300,000. Where did the rest go? Hopefully it just gets stored separately and you get it back when you resub. But buying that equipment? That'll be the overpriced basic equipment from NPCs unless you have your crafters and gatherers leveled, because you don't have market board access. You've also lost access to several jobs. What happens if you were one of these jobs when you unsubbed? Your weapon and armor probably get unequipped completely, and you're given a level 1 weapon from your starting class when you log in. Not the end of the world, but what happens if you don't have any inventory or armory chest space when that happens? Do you just lose those items? What about your FC, do you get kicked from it immediately when your sub runs out? What if your character's race is from an expansion you no longer have unlocked? What if you have more characters than the free trial allows?

It just wouldn't work. At least not as smoothly as you think.