Armcha1r did a stream with Rima last Friday about how NijiEN could be reformed. At about 4 hours it's one of the shorter Armcha1r streams. The general idea is to break potential ideas out into three groups: minor changes that could be done without additional expense or changes to policies, major changes that would require policy changes to enforce, and the real fantasy burn-the-house-down stuff.
I haven't seen the whole thing yet so I don't know if I'm repeating their ideas, but my major change would be to replace all current NijiEN management except maybe at the lowest level and replace them with people who are not current streamers - there should not be any rumors of talents being managers, or having any influence over managers. The "clique" rumors should be gotten to the bottom of and busted up to the best of their ability. Any messages that managers want to send to viewers will come via the managers directly rather than by using talents as mouthpieces as in the black screen stream.
My burn-down-the-house change would be to fire everyone, talent or management, involved with the Zaion and Selen termination notices and the black screen stream immediately, then implement the above.
I can't really think of any minor changes that would be useful at this point, given the scope of the problem.