No idea, but will contribute with some ideas and make some guesses on their price tags:
Not sure if it should be 2 defenders, 2 midfielders and 1 striker - why 2 midfielders, when there's already Herrera and Pogba? And no idea which position Mourinho would want to improve:
LB: Kolasinac - Free, since contract ends this summer
CB: van Dijk - £40m
DM: Saul Niguez - £50m
AM/ST: Griezmann - £90m
£180m for 4 quality players.
Cheaper options on DM could be Kessie (£25m) and ST (Bernardeschi £40m).
Would be:
LB: Kolasinac - £0m
CB: van Dijk - £40m
DM: Kessie - £25m
ST/W: Bernardeschi - £40m
So if Niguez and Griezmann would be impossible moves then this would be cheaper and the 4 players could cost £105m.
Oh, before anyone complains about the figures, just something I think they could cost and to give an idea. Doesn't mean that they'll cost that much or little.
If a RB is much more needed than the LB or CB, than the RB could be Hysaj (£18m). But I Think a LB is much more needed, since it's not clear if Shaw will be ready. And Darmian will likely be sold, so if Kolasinac would arrive - he would share that side with Shaw and Valencia would share the RB with Blind. I have a feeling Mourinho could be in the search for a new CB and if so Smalling would probably be sold.