In no particular order and assuming our preferred formation would be 4-2-3-1:
CM: Frenkie De Jong/Fabian Ruiz
CM: Ibrahim Sangare
CM: Kouadio Kone
CB: Justin Timber
GK: Robert Sanchez/David Raya
RW: Antony/Raphinha
CF: Amine Gouiri/Charles De Ketelaere/Hugo Ekitike
This is not the most perfect transfer window and surely can't be done in one summer, but it would be a good rebuilding start IMO.
Frenkie De Jong is obviously the most expensive one, but once this kind of player became available you don't think twice. We could also fully rebuild our midfield with De Jong or Fabian Ruiz as a backup option if he doesn't sign + Sangare and Kone. I haven't watched many of Kone, but he seems to be more like De Jong back up than a partner in the double pivot, with Sangare and Fred to share minutes. That would be a tehnically solid, energetic and hard-working midfield with various flexible options. Signing all three in the same window will never happen, probably not even in a two, but could free up Garner to have another season with Forrest in EPL.
As for center back, I included Timber as he is heavily linked with us and probably ETH's wish. If he comes here I think he will get his minutes as a center back rather than right-back, but he can also occasionally play there.
Personally, would rather see us sign center forward who is technically well-rounded and can link up with midfield than Nunez who we are linked with. Also, his price tag seems big so he would not be happy being back up for Ronaldo or vice versa. Both Ekitike and CDK are physically good enough to emulate target man role like Haller in ETH's recent Ajax side. With Ekitike practically signed by Newcastle, Giouri would be my pick. He likes to drop to the left to link up and with probably us playing Sancho there that could be a very good link to move the ball in attacking third and also to empty right flank for a right winger and create 1v1 situations for someone like Antony. To add more, when Giouri drops to receive the ball he also loves to switch play diagonally to the right. Not physical enough to be a target man but his hold-up play is very good and he can be a focal point of attack.
If rumors of Newcastle's interest in Henderson are true, we should go for Sanchez for obvious reasons - his dealing with crosses, ability to sweep in a high defensive line and very good distribution. I will add David Raya as a backup option.
The huge risk with full-back options staying the same, but I believe that some of the young players like Williams, Laird, Dalot and Fernandez can improve from working with ETH and then next summer use the budget to target those positions with starting striker and center back too.
Also, I have a belief that young players like Garner, Mejbri, Laird and Amad and others like VDB and Dalot can improve with ETH coaching. All depending of budget size and possible outgoing's, but I'll be happy if we go in this direction.
This team would be good enough to secure top 4 spot and have a good run in cup competitions and also should be competent to play possession-based high line football. These players would inject much in terms of working without the ball and also much-needed technical ability.