I've always thought of it less as the CWE helping us than seeking our aid. What would we need those idiots for?
Of the main ones, Saim-Hann would probably be the most up for it. They seem the most savage of the craftworlds, and they love to go fast.
But like Alino pointed out, the 40k universe is limitless. You tell us.
Dark Angels. The Rock. Lion El "Dwayne" Jonson. I can't be the first person to have thought of this.