While I feel like it could be possible, this will never happen. People enjoy pressing 2-3 buttons for 20+ minutes.

I'd rather SE just not bother, keep the level sync the same to keep the lazy people happy and make some savage-level dungeons instead. 4-player content, required max lvl (so you'll actually have skills) but tuned up so the enemies actually have some teeth. Maybe throw in some one-shot mechanics on bosses. Everyone's happy.