In theory, Big Show should make a good champion. Andre The Giant was the same size, much less agile, and had worse mic skills. But everyone loved him.
Big Show was indeed punished by Jim Ross (who holds much much power in the WWE to those who dont know the backstage politics) and Vince McMahon.
Before the buyout, you could probably muscle Vinnie Mac, but now that he basically holds all the industry cards, its either do what he wants for the price he wants, or go to some low level federation or international wrestling.
In reality, I dont think theres probably anyone in the WWE that would stand a chance against Big Show/Paul Wight in an actual fight. I mean look at it realistically, theres no way Lesnar could take Wight in real life.