i wanted to know what skullface does so important in mgs3 that snake wouldnt succeed the mission without him.
Bullshittiest of bullshits on a silver platter served at a backyard BBQ in Kansas.
If I answered your question, then you'd just come back with some nonsense to "prove me wrong," and we'd do this same song and dance again. So I didn't bother.
But just for the absolute fiddle-faddle of it all, here's an answer to your bad-faith question:
What did Skull-dick do?
Acted as a mole, sending misinformation to GRU soldiers, and real intel covertly to Zero to leak to Biggie.
Cleaned up dead bodies and whatever else Biggie left to keep the enemy off his trail.
Killed soldiers who were closing in on Biggie and got rid of them with his unit before Biggie could notice.
Left shit out for Biggie to get a hold of to use against the bad guys; weapons, ammo, camo, items, the works.
Basically, his whole job was like that of the NSA. Without him, shit probably would've gone sideways or at the very least, been a lot harder for Biggie. But because he and his men did their jobs right, we never even know he was doing it at all; hence the NSA comparison.
He was covertly backing up Biggie from threats that Biggie didn't even know existed, and supporting him from behind the scenes. That's it.
Retcon? Sure. Do I give two camel shits on a hot summer afternoon? Not even a wee bit.