Pjanic-Arthur swap is an accounting operation, financially it will not bring us anything.
I'm not as optimistic as you are, healthy clubs like Bayern, Chelsea, Real don't have to cook their book to invest.
If we want to invest we have to sell our dead weights (rabiot, bernardeschi, rugani...) but as they are unsaleable, we will still be blocked and we will trade with players that we don't necessarily want, for lack of anything better.