If our scouts and Pep think this kid is as incredible as the Benfica fans do, maybe we could do an arranged deal to sweeten the Felix transfer. Offer them the money they'll want in 6 months, but let him stay there for the year and he can come in and replace Fernandinho in the squad directly.
Would also guard against a transfer ban, as pre-arranged transfers are allowed to go through even in a banned window. Plenty of room to get creative as we're in a position of relative strength with the squad as it is.