From a 2nd Amendment standpoint, this kind of split would be great for most of the states involved. You would be splitting off California, which dominates the 9th circuit, and Hawaii, which is even more anti-RKBA than California if that is possible.
Then you have a new circuit of very pro-2A states--Alaska, Montana, Idaho, Arizona, etc. It never seemed fair to them to have Cali judges deciding their cases. This split would minimize the influence of the heavily anti-gun 9th circuit in my opinion, since it would represent many fewer people.