You know Coutinho and Seri would be nice.
Iniesta, Busquets, Rakitic, Roberto, Coutinho, Seri.
Would keep Samper, but they won't keep him despite some decent performances. Sell Gomes, sell Rafinha too. Obviously Arda can just leave, and Denis can be a LW/RW/Wherever he's needed backup.
Didn't include Alenya for obvious reasons as he'll continue with Barca B and get called up regularly. When Iniesta seemingly leaves/retires after this season, he can take up his spot in the squad.
That's not a bad midfield in depth too. Can slot in Denis there if needed and call up Alenya too. Can put up Iniesta-Busquets/Roberto-Rakitic or Coutinho-Roberto/Busquets-Seri
Can rotate more without a huge drop in quality. Also Seri not being a high profile player means the club can move on from him if other players eventually turn out to be better or more worth keeping.