IMO the best way to make a stand-alone Hulk movie is to have Bruce Banner hired to investigate a feral, seemingly unkillable man in the Canadian wilderness. AKA the Wolverine
In a sort of the inverse of the animated *Hulk vs. Wolverine,* the government hires Bruce Banner to investigate a claim of an unkillable man that is causing some issues up in the Canadian wilderness. Wolverine has lost his humanity and is living ferally in the mountains. The Hulk is needed to bring him in.
This could serve as The MCU's version of the Wolverine introduction. Having the two classic characters clash on screen would be a perfect way to set Banner apart in his own story and have a greater X-Men presence movie into the next Phase.
Having these two face-off in tree-smashing, boulder-destroying, earth-shaking battles and eventually Bruce helping Logan connect back to his humanity would be Fantastic.
<a rel="noreferrer nofollow noopener" href="https://www.marvel.com/characters/wolverine-james-howlett/in-comics" target="_blank">https://www.marvel.com/characters/wolverine-james-howlett/in-comics</a>