Here is what I would do...
Sell for whatever we can get: Coutinho, Dembele (if we can't sell then loan him to get rid off his wages), Vidal, Umtiti, Busi and Suarez (I know those last two will never happen but one can hope)
Buy:
1. Upamecano - around 60m
2. Isak - 50-60m should do it
As already mentoned these two are my priorities. And then further:
3. Camavinga - around 60m
4. Aouar - around 50m
5. Mertens/Willian - free transfer, contract shouldn't be longer than 2 years though
6. get back Todibo - don't think S04 will buy him; IF they will get Salisu from Valladolid as a 4th CB for 12m. Or regardless get him anyway, I really like his potential and getting another CB would also give us an option to play with 3 at the back which Setien likes. And I think Pique could retire in 2021 so we'll need another CB by then anyway.
7. Would also like to bring back Emerson though don't think it's possible so Semedo will stay a starter for another season (don't really like him but we have other more urgent needs). But we can get that Porto RB for 10m and give him a chance in preseason to see if he's ready for a backup role. If not give him a few months in Barça B to adapt and then promote him.
If we can't get rid off all amigos get Frenchies in so we'll have another "clique" to go against them.
http://lineupbuilder.com/?sk=v5fy9
1. I would still keep Pique as a starter as I think he would look a lot better alongside a faster CB like Upamecano. But Todibo should get enough minutes to show what he can do. Lenglet is good enough for a 3rd/4th CB role and I'd keep him over Umtiti because he's still more reliable/less injury prone.
2. Firpo starting over Alba won't happen but I think he'll do well if given prolonged playing time to adapt to the team and build a confidence. I'd play him a bit further up the pitch as a LWB since he's more used to this role. On the other hand Semedo would be more defensive (I know some people are high on him but I really don't believe he has enough attacking quality, he's solid defensively though) to give us more balance and also to cover for a slower Pique. Upamecano can cover for a more offensive minded Firpo/Alba on the other side.
3. Camavinga and FDJ could exchange their positions in the buildup but Frenchman is better defensively so I'd play him as a DM. Busi should be strictly a backup though with Setien he'll likely still start most games. That's why I'd sell him and keep Raki (if he'd accept a bench role which he won't anyway) or just give a chance to M.Fernandes.
4. I don't see Arthur as unquestionable starter so I'd rotate him at both CM positions.
5. Aouar is a bit of a forgotten man here lately but I still like him very much. He can bring goals and assists and also ability to play as a LW.
6. Forwards are all versatile so we'd have multiple options. Playing Messi behind Griezmann-Isak in a 4-3-1-2, they both can move to the left as well. I think Trincao can also play as a false 9. 4-2-3-1 and 3-5-2/3-4-3 would also be possible with these players imo.
7. Willian or Mertens would bring some veteran cover for youngsters Fati, Trincao and Isak.
I don't know if this plan would work but I'm sure it would have better chances to succeed than what I'm affraid we'll do. Buy Neymar for some stupid money and hope he'll solve all our problems while going into another season with Pique and Lenglet as our best CBs and Suarez as the only true "9" (we'll probably extend his contract as well because that's what Messi&amigos want).
