At first, I didn't know why Heavy Weapons Guy was brought up in the first place, but then I realized this is the Roster Discussion Thread.
He has no chance, therefore he's not even worthy of being discussed. It's pointless to argue about a character that doesn't meet Sakurai's criteria. What's so hard to understand about this?
Before someone brings the "Sakurai can change his mind" argument, let's not forget that he was very strict regarding third parties. He clearly doesn't want to add any third party, since it would lose the focus of the game.
Sakurai said:
“I think Snake and Sonic joining were fantastic. It made many fans happy, and it broadened the Smash Bros arena. However, introducing more non-Nintendo characters willy-nilly will lose the focus of the game, so I also recognise the need to narrow it down.”
So far, Sonic and Mega Man are in, but they are major video game characters, recognized both in and outside of Japan. Snake is the protagonist of the Metal Gear series, which is also a very acclaimed series and Snake is a well known character.
Heavy Weapons Guy has nothing of that, not to mention he's never appeared in Nintendo consoles. The fact that he comes from a Western game doesn't help either, since most Western games don't do well in Japan.
Long story short: Heavy Weapons Guy won't be in due to not meeting Sakurai's criteria and anyone who thinks otherwise is delusional.