Potential plot for the Hulkbuster:
Based off the assumption that the ‘Incredible Hulk’ movie is part of the MCU, I think that Banner and Stark working together will have serious implications. Let’s look at what we know:
First: both through the comics and the Incredible Hulk movie, we know that Banner wants to at least be able to control the Hulk, if not cure himself of the gamma radiation.
Second: but wait, didn’t they develop at least a temporary suppressant for the Hulk in the Incredible Hulk movie? Yes, they did! However, this treatment had to be administered through IV before Banner transformed, which is obviously not a solution for when he’s already the Hulk.
Third: They’ve portrayed Stark and Banner as somewhat kindred, misunderstood genius, spirits. Stark clearly wants Banner to be able to treat the Hulk like he treats his suits, ie: something he controls with choice and agency. They also both realize that there is some seriously bad stuff out there, and eventually the Hulk will likely be needed to protect the Earth. I am of the mind that Marvel typically has a motive for their choices, especially the One-Shots.
Conclusion: Stark and Banner collaborate on both the Hulkbuster and an improved suppression serum. It would likely take getting close enough to the Hulk to deploy some type of shot or aerosol shot to the Hulk, and then live long enough to see it take effect! Thus, the need for the Hulkbuster suit! So, Stark helps Banner solve the problem of creating a serum that can viably work in an outbreak or ‘too angry to quit’ scenario, while Banner helps Stark develop a Hulkbuster suit that is capable of hanging with the Hulk long enough to use it. Thoughts?