Can you claim BAH from a different location if your family stays at one location and you move?

An approval process exists, but the likelihood of it being approved is minimal. You might be able to strengthen your case if you go ahead and submit a retirement packet (if you haven't already done so). You could make a financial argument that the costs of the higher BAH are offset by the elimination of PCS costs of moving your family and HHGs stateside, and then back to Hawaii upon retirement (or wherever they base your HHGs shipment costs for retirement). I doubt they'll do it just for convenience purposes that are based on a stated desire to retire on a specific timeline (but not with a retirement packet having been submitted). We have all seen examples where people say they are going to retire to get what they want from the military, but then don't retire once they get what they want.

You can apply for a BAH waiver based on a legitimate reason for your family to stay in place.
It's not subjective, as there are specific criteria, but it is case by case.
It can be disapproved, but I have not seen that happen yet out of a few dozen.
If granted, it's a year to year thing, but sounds like you only need the first year.

No, you can not claim BAH for both the location of your family and your future duty location. Although there is an appeals process, I’ve only ever seen it for senior individuals whose spouse or children require extensive medical care that can only be provided at their current location. You mentioned it’s only because Hawaii is the location you want to retire to, which does not meet the requirements to obtain dual location BAH. As a LTC, you are also NOT authorized unaccompanied housing and your BAH will be tied to your physical location, not your families location. So you have 1 of 2 options: 1) move your family with you 2) pay out of pocket for the residence in Hawaii.