All this discussion reminds me a South Park chapter...

Cartman's mon: ohh look Toshiba handibook, same hardware and does everything the Ipad does, but half the price...
Cartman: yes, but it's not an Ipad...

So I guess Rogue could be a thief clone, have all it's traditional skills/traits, be played like a thief always was played....then you get a soulstone for ninja (like you know, ninja being an advanced class for thief in lots of FF games), still has all the thief traditional skills/traits, still hold the same thief playstyle....but is not called "thief"....the horror....

If it moves like a duck, acts like a duck, quacks like a duck....then is a duck even if I dress it up like a cat...