[long thread warning; for a TL;DR section as a sum up of this thread look at #1]
100 Thieves' biggest issue lies in the incompatible playstyles of their players which eventually leads to them being uncoordinated. This problem is most likely rooted in many little roster changes in a short period of time that ruined any progress and team chemistry created. Strategy-wise, the team lacks discipline, coordination and ability to play post-plant situations efficiently. As previously stated, all of the little problems could be fixed with players getting used to each other and adapting to each other's playstyles and tendencies. However, leaving the roster as it is wouldn't be the most efficient solution and definitely not a viable long-term option/solution. Here are some viable options for the future.
1) Building around Asuna
Peter has proved himself a star on many occasions. He is more than capable of entrying the sites and creating a lot of space for the team whether he is on Jett or Raze, depending on the map. If Asuna is your Jett main, plus Raze on some maps, this team should focus on getting a primary Sova (or some other agents for Split, Fracture) - meaning, dropping Hiko could be the play here. Ethan could stay if this is the case but should be relieved of the IGL duties & he would be mostly playing Chamber or other sentinels if necessary.
[Potential roster: Asuna, bang, ethan, drone, Ange]
2) bang & Asuna duo
Both bang and Asuna are very young and promising talents that have a deep understanding of the game. They both are capable of applying early aggression on defense to pick enemies apart or enter the sites using their own or their teammates' utility is almost unmatched. Them playing off each other and having other players on the roster that allow them to utilize their game knowledge and mechanical gifts could be a recipe for great success. This probably wouldn't take too much time to be realized.
[Potential roster: Asuna, bang, koosta, bjor, drone]
3) Rebuild mode, young core
Solution for 100T problems could also lie in them keeping the essential pieces for a winning team (one experienced and proven player + a star fragger). This would mean that only Ethan and Asuna should remain on the team and go back to the drawing board trying to figure out the missing pieces with their management. Them taking their time, trialing players, using team-building activities like bootcamp and trips for chemistry could potentially lead them to a long term success they so desperately strive for, and in my opinion, this could potentially minimize the roster changes that ruin team chemistry often.
[Potential roster: Asuna, ethan, aproto, bjor, Ange]
4) Coaching
In any case, drop the coaching staff and at least start fresh from there. Sign Sean "sgares" Gares as an analyst.