Nah, still broken m8. Also, it doesn't seem that there's any way to get past the Ability issue. That's okay, I have another idea I'd like to share:
Hidden Dynamax
Premise: In Gen 8, Hidden Power was done away with. However, Showdown still has the old formula in place to calculate based on IVs. If only we could utilize this in some way...
It turns out we can! In this mod, the Pokemon's Hidden Power type will be relevant again by activating whatever Dynamax effect a move of the same type would activate when the Pokemon enters the field.
This may break some mons and would require some bans, which seems like it might contribute to a healthy discussion.
I really like this one better than "Dynavolution" as Dynavolution would probably be an incredibly broken meta, and I also can't think of a way to implement Hidden Abilities.
This meta could get rid of Dynamax altogether and would still be possible, unlike Dynavolution, as well.