The easy solution would've been to bring Hulk and She-Hulk into the mix if they were dead-set on this The Incredible Hulk 2 starring Sam Wilson approach. The movie would've felt more like an event, She-Hulk would've gotten some badly needed screentime, and those two could've handled the physical side with Red Hulk, making the final battle a lot more exciting. It could've played a bit like the Trinity fight from BvS, with Cap taking Batman's gadget approach and ultimately delivering the final blow similarly to how it went down in the film anyway.