Honestly this is quite a lot, and I also share the same sentiment as you here, their are some players in this list that may be very useful to this arsenal team, but if this news is actually true, then they really have to splash the cash also, because they can't let a whole lot of useful players leave the club and not replacing them back, so that's why I believe that they must splash the cash in this summer transfer window if something like this happen, because since they will be going for a more quality players, It would be more expensive compared to how much they will make selling out this players that are no longer needed in the team.
Another department in this arsenal team that seriously needs to be addressed is their striking position, they really need to sign an attacker that would guarantee them 20+ goals a season in other to be able to compete very well for the league title next season, the mistake they made this season should not be repeated, because in my own opinion, that was their greatest failing this season.
I am not also a fan of selling a large number of players at once. The club could make mistakes and sell a player who would have been a great asset in the future. Some players are not doing well because they have not been given enough opportunities. Arsenal should do a reanalysis to determine if they really need to sell all these players. But if it will help them finance the buying of better players, it will not be a bad idea. But I have seen clubs who later regretted selling some players because they later improved drastically.