Doing the center back seam, 1 1/2" is about right.
But if the price is not a consideration this can be done.
the entire waistband is removed. Then the waist is taken in a number places
around the front and sides and back. the band is shortened and replaced.
It takes a good deal of time and that is what alterations are charged for.
Talk to your tailor about this.
Are you saying take the waist in from the center back seam is the easiest and cheapest way to go or just as expensive?
Sorry if I phrased this badly. But taking in the center back seam only, would be the cheapest.
The more complicated job would take a great deal more time and cost much more.
But then the waist could taken in far more than 1 1/2" and not change the appearance of the back pockets.