Realistically we have more then 6 players who either need to/ want to or contract is running our or so are going to leave so keeping it to 6 would mean keeping a lot of players who we need rid of in the squad:
Players leaving through end of contract:
Valencia
Mata
Herrera
Out of these really only Herrera is worth keeping, but think he's got his heart set on leaving. if Mata is happy with a 1 or 2 year deal on reasonable wages i'd keep him but he's likly to want a longer term deal and he realistically shouldn't be part of our plans in 2/3 years so we should let him go.
Dead wood players who really we need rid off:
Darmian
Rojo
Bailly
Players whose want to much money to stay and arn't performing and seem to be giving the team a bad attitude.
De Gea
Pogba
We also need to get rid of Sanchez, he is messing up our wage structure ridiculously and its just embarrassing we need to draw a line under it and move on no matter how much it costs us short term.
So leave:
De Gea: £35 mil (last year of contract maybe lucky to get that)
Pogba: £115 mil
Mata: Free
Sanchez: -£20 mil (realistically if we want rid of him we are gonna have to pay off a lot of his wages which maybe around 20 million)
Herrera: Free
Baily: 5 mil
Rojo - Free
Darmain - Free
income = £130 mil
Thats 8, and all we can realistically expect to leave in one summer, and it would still leave quite a few players who we need to move in the next year or so either cos of age (Young & Matic) just arn't really good enough (Smalling/Jones) and players who havn't quite performed to the level we had hoped yet (Lukaku/Lindelof/Fred). So we still have a lot of work to do. So i don't think we can afford to let less then these 8 leave, it will just leave us to much to do following summers.
As for bringing people in, i've done this based on the idea that we arn't gonna compete next season and need to think about building a squad that might be able to compete in about 3 years, so no players over 25/26.
Signings:
Rice: 75 Million (We need some captain material in midfield he's it)
Felix: 104 million(release clause) we need creativity, he is hands down the best on the market.
de Ligt: 65 mil, the Best young center back on the planet and a leader. Likly off to Barca though so would go for: Milenkovic (40 Mil)
Tielemans - 40 mil (need some creativity in midfield if Pogba goes)
Sessegnon: £35 mil, disappointing season, so will be cheaper, has bags of potential can play either full back or either wing
If we had any money left I'd also sign Brandt for his rumoured release clause:
Promote/Recall from loan:
Henderson
Tuanzebe
Greenwood
Chong
Gomes
Which would Leave us with:
Goalkeepers
Romero, Henderson & Grant
Fullbacks:
Shaw, Dalot, Sessegnon & Young
Center Backs:
de Ligt(or Milenkovic) Lindelof, Tuanzebe, Smalling & Jones
Midfilders:
Rice, Tielemans, Mctominay, Fred, Matic & Pereira
Attackers/Wingers:
Felix, Martial, Lingard, Chong, Gomes, (Sessegnon) (and maybe Brandt)
Strikers
Rashford, Lukaku & Greenwood
Not a finished squad by a million miles, and no way near ready to compete for the premier league, but a squad that would starting to have pieces in place we could build on rather then just tearing it up every summer and spend ages talking about deadwood.