Kojima himself already asked for Snake to be in Super Smash Bros. Melee, but Sakurai trurned him down for being too late. So he tried again for Brawl and Sakurai gave it some thought, which resulted in having Snake for Brawl.
But Sakurai can be very picky at times. He recently stated that the roster for Super Smash Bros. U/3D was set near the beginning of development, and that fan input had almost no impact on it.
So, I guess PLOK could become a DLC character, but I fear he's not iconic enough for Nintendo to get him in. And if he was planned, Sakurai would've called you already... wait, did he?!
Comment by Guest Kaze_Memaryu, added Thu, 17 Jul 2014 21:22:30 GMT