To me, our mercato from here is binary depending on whether Pogba stays or leaves.
If Pogba was to leave, he would generate a one off profit of around 110m + savings of 9m in salary = 120m in year 1 and 9m in Year 2.
With a Pogba sale, we would need to invest some of that money on say, 1 replacement. Lets say that replacement costs 25m, 5 year contract on 3m net = 11m per year.
So saving net saving in Year 1 is 109m and -2m in Year 2.
Should we keep Pogba, we may need to raise his salary by 3m net or 6m gross. But there would be no need to bring in a replacement. The profit we could garner from his sale could be postponed to a following year.
My sense is that sacrifices would need to be made in order for Pogba to stay. It may require the sacrifice of Lemina, Pereyra and Hernanes. Lemina could generate us a profit of 10m, saved amortization of 2m, plus gross salary of 3.5m = 15.5m. Pereyra would equal 15m (assuming he is sold for 16-18m), Hernanes would save us 8m even if we sold him for 6m. So Pereyra, Hernanes and Lemina combined would save 38m in Year 1 (covers the 1st year cost of Higuain which is 33m) + the additional wage for Pogba.
If our midfielders are: Khedira, Marchisio, Pogba, Pjanic, Sturaro, Asamoah, Mandragora - I think that should be fine. If we want additional depth, it would be best to find an up and coming young midfielder who is under 21 so that it would not breach the quota and could potentially be another hidden gem.
Pogba' huge profits will be available for some time given that he is still very young. His valuation would not go down much from here.