Meh...not cloned, really; more like composite construct or something. Recall that, while Firion's EX Mode is a boost to his weapon (Blood Weapons), his EX Burst is something close to Omnislash Version 7; both are composites of two different, general types (EX Mode is something between Cloud/Tidus and OK; EX Burst is similar to Cloud).
Vaan will, thus, have a fighting style sorta like Firion (except that he may unleash different weapons such as hammers and guns, which are absent in FFII) and perhaps his "ever-changing" style will include some magic or work in a way that resembles Licenses. Not sure about his EX Mode (Unlocked License?), but we already know his EX Burst will be exactly like Gabranth's (Mist Knack, unless for some reason they've decided to change it).
But then again, Vaan is just there because they want to shoehorn him as the FFXII representative given that he's...sorta...the main character. Not enough guts to get Balthier, whom would have charmed the game with his presence (plus a scene with Locke AND Balthier...scoundrels ahoy! ...What!? No, of course it's not in a shipping way, it's in a bros before Ho Hos way!).
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