The connections between the two stories are pretty tenuous, really. Sure there's an empire and some rebels, there's an urchin-turned-hero (kinda, though Vaan's not really the saviour of the world or anything), a slew or aerial battles, and the final dungeon is a [spoiler]giant, super-powered combat fortress[/spoilers], but that's about it.

If some of the environments looks like something out of Star Wars, that's because those films used a lot of real-world locations too. FFXII's architecture is based on a lot of actual cities.

The Viera environment closely resembles the film version of Tolkien's Lothlorien, more than anything from Episode III.

Floating islands are nothing new to fantasy; anyone who thinks Episode V invented those ought to broaden their reading a little Aside from the fact that both are floating and both involved in some kind of mining, Bhujerba and Cloud City are completely dissimilar.
Mt Bur Omisace is a mountain, so it's covered in snow. Just like mountains in real life. Doesn't make it a Hoth reference.

Penelo is an upbeat support character, there to watch out for Vaan and constrain his recklessness. Completely at odds with 3PO. Obi-Wan and Basch are also as dissimilar as you can get, in terms of their role in the story.

While there are some similarities, and some things showing a definite influence, I don't think it's fair to say FFXII was actually based on Star Wars. The same could apply to virtually any epic, quest-based fantasy story, including most of the other Final Fantasy titles.