I don't remember what site it was, but I remember being on a forum once where the tables could be set via ratios. I don't know if something like that would be an option here?
I think tables get pretty non-functional on mobile as it is, since, if you've got, like, 4+ columns they display as barely a word wide. They don't break the post, but they become practically illegible.
Would setting the table widths break the mobile view be a thing where it would stretch out the entire post, or, like poke out over the edge? Could it be a thing where, like, a too-wide table could display with a side scroller bar without breaking past the post edges?