I've never seen that proposed. That would be a very interesting scrap. To answer OP's question, I would favor Povetkin by stoppage.
Styles make fights. Povetkin was hittable . Shavers, arguably the hardest puncher of all times, clips him probably sooner then later and then it is game over
Povetkin. Shavers has the power, but Povetkin has literally everything else. With the caveat that Shavers always has a chance, you'd have to favour Povetkin heavily based on how consistent he has been.
And who did Povetkin ever defeat who had power...Donald, Byrd, Chambers, Charr? He got dropped often and stopped when he faced punchers in Wlad and Joshua. Shavers annihilates Povetkin who isn't all that hard to find.