9. Nicolas Cage
Give the people what they want!
Nic Cage may not command the star power he used to, but if there's one thing he's always had, then that's the people's vote.
Cage's often wild and erratic performances have led to him becoming an icon. His wild faces, over-the-top shouting and unhinged nature make him an absolute delight, and even when he's toning it down to "get serious", you can still feel that wild streak in him.
So, seeing him in The Expendables 4 would be like a firecracker going off. His wildness would blend well with the bombastic style of the action series whilst also making his character stand out against the severity of the other celebs.
He's got plenty of action credibility and a screen presence that cannot be ignored - with a trio of action classics in the nineties to his name including The Rock, Con Air and Face/Off - which is why he'd make a hilarious, yet appropriate addition to the cast.