I can see the club not re-investing the majority of this money really... And looking at the rumoured signings I'd expect that to be the case actually. For what it's worth, I think we'll get more like £130m for Pogba, but I'll go with the £150m for the sake of the thread. This is what I'd do personally assuming certain players just aren't available and I can see it not being too far off:
Sell: Lukaku (£75m), Pogba (£150m), Darmian (£10m), Rojo (£10m), Valencia (Free), Herrera (Free)
Total: £245m
Buy: James (£15m), Wan-Bissaka (£45m), Longstaff (£20m), Alderweireld (£25m), Fernandes (£50m), Ben Yedder (£35m)
Total: £190m
I think that gives us a good enough platform to finish 4th and leaves us £55m in the green, not even touching the supposed £100m+ transfer kitty for the Summer. Of course, if there was another CB available and we could break the bank for say, Sancho, then I'd love us to sign him and fill that void on the right wing. Maguire looks very possible, but I personally don't want him at United. I'd love De Ligt but I think it's out of the question that he comes to United for example. If this really was fantasy league (I assume that's the general gist of this thread), then I'd probably just blow £80m+ on Sancho and try to twist Dortmund's arm. I don't think I'd 'settle' for Maguire, I'd roll with Lindelof + Alderweireld for 2-3 years, developing Tuanzebe and trying to find the next big thing at CB after De Ligt while we get the last top seasons out of Toby.
Although, someone I really want us to sign is Ndidi. He'd probably be available for anywhere between £40-60m I suppose? Him and Sancho added to that buy list would be awesome, though I think we'd still be missing maybe one quality CM.