Agree with everything. Lemina is developing in front of our eyes. Box to box is clearly the best fit for him, but at the moment he's also the best DM we have.
We still need a technical player who can create goal opportunities for the bench, when Pjanic can't play. I dont think Witsel fits the mold, from what you've said. And we need a DM to rotate/compete with Marchisio, freeing Lemina to play at his best position.