While it is theoretically possible, those kinds of accounts are incredibly rare. I wouldn't recommend going for that.120% requires you to have full Water Eidolons equipped, which means less base Atk, which means not-quite-120%. The difference between 100% and 120% is quite meh.
... which is why they're buffing 120% Eidolons to 140% (up to 160% I think it was?) in December. That's when the difference becomes noticeable. Until then? Nobody cares.