mandibula can easily expanded up to atleast 1cm with expander, no problem whatsoever.
I acknowledge your point and I know you had this done so you speak from experience. However, the only methods I know of are MSDO (distraction) and SFOT (layering bone paste onto the alveolar area in order to allow maxillary arch widening with braces).
I’ve gotten the impression that doctors in the US aren’t willing to do MSDO for non-syndromatic cases. Doctors in Europe seem to be more open to doing it on non-syndromatic patients.
As for SFOT, there aren’t too many doctors doing it in the US.
Overall, in the US, it’s theoretically easy to do but unfortunately not so easy to get it done unless you happen to live near a doctor who does SFOT or are willing to travel to another state.
If OP is in Europe, he might have an easier time trying to expand his mandible if it’s at all needed.