I think the best thing they did last summer was cleared the average players out. Hart, Cabellero, Nasri, Sagna, Zabaletta, Fernando, Navas, Bony, Clichy etc all went and some of these guys were good servants others were expensive flops, they even sold a good youngster in Iheanacho because they'd upgraded him with Jesus.
It meant Pep didn't need to mess about trying to keep guys happy to maintain squad harmony they were ruthless and most of them left on a free those who wouldn't go went on loan.
They even tried to get Evans so they could send Mangala on loan but it didn't happen so they were forced to keep him I think the only guy who left that Pep wanted to keep was Kolarov but he wanted to go back to Italy and he didn't want to be a squad player. There's talk that they'll try and sign Bertrand or Van Aanholt in January because they need a left back with Mendy out for the season.
I think at the start of the season there were 4 first team players that they couldn't really replace with quality if they got injured Ederson, Stones, Mendy & Fernandinho. I think that's still the case but for the other 7 spots they've got at least 2 options.