These might not be like for like exactly but as you asked it's what I'd do: -
Pereira - Angel Gomes (it's a missed opportunity with Pereira it looks like, I don't want him to go but he wants out due to lack of first team minutes).
Fellaini - N'Dembele/N'Didi (WWhen Matic doesn't play we need someone industrious to sit in that midfield and set the tempo)>
McTominay - Promote another youth player or keep one of TFM/Tuanzebe in first team next season. They are not CM's but can cover different positions.
Sanchez - Get a Right Winger like Carrasco (apparently available?), keep Chong in first team to compete for that right side spot next season.
Young - I've thought about this more and think he deserves one more season because he can cover LB fairly well. bin Valencia though.
Mata - I don't think we need a direct replacement for Mata, he plays on the right and I've addressed that in other players. Pogba free role goes into no.10.
Darmian -/Valencia - Dalot first teamer but get a more competent RB instead of Valencia to compete for the spot. Not sure off the top of my head.
Jones - Too error prone and many niggly injuries. Get Koulibaly the only commanding CB out there we can get that will have an impact on and off the pitch.
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All in all I'm just saying that we need to get rid of deadwood and replace them with more competent options to compete with youth we should be pushing through and other players like Dalot net season rather than Valencia.
Make 3 good squad additions like N'Dembele to bolster the midfield if we get rid of McTomiinay/Fellaini and add some industry. Get a proper right winger (Carrasco was just a realistic one that sprang to mind but there are others) and bin Sanchez/Mata who we always try to shoehorn into this side. Promote Chong to offer competition on that right side and promote Gomes to replace Pereira. Bin Valencia as he offers nothing on that right side and we need a more competent RB going forward to compete with Dalot for that spot. I'm not totally convinced by the names I mentioned above for the RB spot, but we just need someone who is decent all round and they'll be an improvement on this Valencia.
Finally, my 1 world-class signing and high value would be Koulibaly because he is the only guy that could improve our defence and add some much needed leadership on/off the field.
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