I still kind of think putting Deadpool into the MCU is a bit of a mistake.
Once you have a character who breaks the fourth wall in such a pervasive way, I don't know how we can buy into any dramatic or emotional stakes in the MCU anymore. It's why I similarly don't think She-Hulk should do it on her show.
The only workaround I could imagine would be that, if Deadpool appears in non-DEADPOOL films, other characters react to him as if he's mentally ill/schizophrenic, constantly talking to be people that aren't there (i.e. the DEADPOOL movies are from his perspective, so when he breaks the fourth wall, he's talking to us, the audience, but in other movies, he's giving random asides to nobody, and not directly to camera).