Reckon the combination of Sancho and Chiesa would be good for implementing the style you want, mate — one in the summer and one in 2020 — something along those lines should be doable, and will hold us in good stead over the long haul. Sancho is more decisive and gifted obviously, and needs no introduction on Redcafe because practically everyone wants us to sign him, and for good reason, but Chiesa also has a great skill set and could emerge as one of the best wingers of this generation, and is showing considerable potential at Fiorentina with 16 direct goal involvement in 2018/19. Plus, he's quite industrious and tactically astute for his age (which signals that he could be molded along the lines of Ribéry), and despite being wingers in generalized way, both Sancho and Chiesa are different enough to bring an eclectic mix of features to the team — on top of being comfortable on either flank and having the ability to switch the ball diagonally/horizontally (which was a key feature of Bayern when they head Robben and Ribéry at their peak).
Though one thing to bear in mind is that Bayern had Alaba and Lahm as the supplementary outlets for Ribéry and Robben from deeper positions, Müller as the raumdeuter to create room for them, Mandzukić as the foil up top, Schweinsteiger's distribution — and an overall scheme that was very well drilled and compact in two banks of four, mostly notably under Heynckes. That provided the perfect environment for “Robbey” to thrive, and for Sancho/Chiesa to excel at United, we'd have to strategize an effective scheme around them in similar fashion. And we'll also have to be patient because they have an average age of just 20 (for reference, Ribéry was 24 when he joined Bayern and Robben 25, and they still took a bit of time to reach peak levels). In an ideal world, we would have immediate solutions, but because we missed the last 2-3 mini-cycles to acquire the best players, we'll have to be more forbearing and methodical in our approach, especially considering there's a dearth of prototypical wingers in contemporary football.