Thirteen issues is a little thick for one TPB, but since it's the Hulk, why not a Green Goliath-sized trade paperback? For the cover, some of the later covers are beautiful, and the one from What If General Ross Had Become the Hulk? is an awesome candidate. I think I'd rather go with What If (1977) #23 though, because the Hulk as a barbarian makes for an awesome idea, as the Planet Hulk story arc can attest to.
Would you buy it? Let me know in the comments, and thanks for reading.