Too hard? No, it's just a FF title, and the appearance is just a graphical style - they've got shit drawers if they can't bring that to a current-gen title.
Too much work? Not more than other FF titles, they just have to make an investment which will pay itself back within a few days with Japanese sales alone. They could probably get away with half-assed graphics that take half the time to create too and release it as a budget title.
It's not a matter of too much work, too difficult, that they can't work with the PS3, it's economics, pure and simple - they need a higher-up to decide on investing a few dozen million on it. FFXII cost $35 million, for example - they could make it an excellent game with just half that.