Raiden is in Sony Smash. So Metal Gear is represented there, technically.
Yes, with classic Sony characters such as Big Daddy and Isaac Clarke.
But you know what I mean. The two biggest PS1 characters and they're in the Nintendo games 
Just like Ryu and Cloud are classic Nintendo characters. 
More sword dudes in smash, just what the game needed.
In all fairness, Street Fighter II was a big deal for the SNES. Cloud is definitely the outlier though.
EDIT: If it were upto me though, I'd probably gone for Black Mage or something. Dunno what really fits FF the most for Smash Bros, but I kinda figure something from the early titles would suffice.