I suggest putting a clone of Luke in a tank on Exogol. That would imply the Luke we saw in TLJ was actually a deranged clone - maybe Luuke from the Thrawn Trilogy survived and tried to train some Jedi.
That’s hilarious and I kind of actually like the idea but would prefer it to be a clone of Palpatine. That way no gravitas is taken away from Snoke while explaining how Palpatine is still annoying the Galaxy.