I don't think it's crazy at all. It would also be 28 million off your wage bill each year. Olise you could probably pay 6 million per year or less. Although I think Sancho could be as good as Olise, he won't be at Man United. Plus Olise is younger.
The trouble for Man United imo isn't signing players but offloading some of the players who are on big salaries. If you can do that it creates a lot of maneuverability for signing new players. I'm pretty sure Ineos will stop the practice of paying huge wages anyway, which will free up a lot more money for transfer fees. Just your top 7 earning players are costing 100 million per year (Casemiro, Varane, Rashford, Martial, Mount, Bruno, Antony).