No. I've thought about this before too. I never thought I'd approve of Dissidia's style but it works and is the only way to represent the unreal awesomeness of the characters. The only way to stay true to both games would be to go the route of Monty Oum.

Characters from Final Fantasy could then be pitted against combatants from Soul Edge/Calibur and Tekken (due to being made by the same company and sharing the character Yoshimitsu). The only question here would be where does one draw the line as to what is and isn't Soul Calibur/Tekken. Link, Necrid, & Spawn have cameoed in Soul Calibur. Tekken is crossing fists with Street Fighter. Do we toss Link, Necrid, Spawn and Street Fighters into the fray as well? Obviously the Street Fighters are unnecessary as they can star in their own crossworlds in something like Fantasy Fighter.
But I see no other way in which Link or Necrid or Spawn would end up fighting Final Fantasy characters.
Starkiller, Yoda, and Vader, on the other hand, have the same deal as the Street Fighters. At least Vader has already been featured in a Star Wars fighter called Masters of Teras Kasi (TearAhs KAhsie: a fictional martial art known only to the Emperor's Hand: Arden Lyn) along with several other characters including a Tusken Raider (sand people) named Hoar.

Complete cast of Teras Kasi:
Luke Skywalker
Darth Vader (must be unlocked)
Han Solo
Princess Leia Organa
Chewbacca
Arden Lyn
Boba Fett
Stormtrooper (must be unlocked)
Hoar
Thok, a Gamorrean guard
Princess Leia (in Jabba's slave outfit)
Mara Jade (Emperor's Hand)
Jodo Kast (Mandalorian wannabe)

Personally, I'd love to see Final Fantasy characters teaming up to try taking down General Grievous, not to mention pretty much any Sith.
Anyone noticed that in Monty Oum, we've only seen Final Fantasy HEROES? There hasn't been a single villain despite the fact the DOA cast so far includes the good, the bad, and the undecided.