Dont know about all you suggested here but Keita could be a revelation if he improves further while we still need to add something in central midfield and as for wingers Keita is not enough we really should push hard for Sanchez as Sanchez could give us the thing we are missing upfront!
In fact the best mercato (even though impossible one) is:
2 wingers who are fast move a lot and create things out of nothing as well as score - Mbappe isnt a winger but he would be amazing on the left while Sanchez would be amazing here too
CM - Verratti and a strong physical midfielder who can also make some offensive work as well as defensive work
This alone will cost us around 300M so impossible
The easier scenario although still difficult is: decide if we play 4-2-3-1 4-3-3 or 4-3-1-2/4-3-2-1
If we play wingers Sanchez and Keita are the ones if we play 4-3-3 or 4-3-1-2/4-3-2-1 Sanchez could be the one and only addition there
CM - Its obvious we need someone for possession and also muscle so Verratti would be nice but we would still need someone who can add some muscle and even Nzonzi could do the needed work (Bringing Vidal back would be the ultimate though)
Sanchez will cost 50M while Verratti 80M and Nzonzi/Vidal 30M-40M I guess - it will be lots of money but with CL final and some sales we can do it...
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I've heard a lot about Fabinho but Bakayoko should be explored as well. Love that guy.
Bakayoko is interesting but he seems to have a trouble with passing under pressure (at least against us he had 2 bad games IMO)