Sounds like a plan, MJ . . .
Should work out fine. When I got into this game, I picked up a box of 20 g. pins and a box of syringes with 25 g. 1" needles, figuring that I'd use the 20 g. for oil-based shots and 25 g. for water-based shots.
Why 20 g.? Because as I read about AS, that's what the manufacturer of Delatestryl (test enanthate) recommended. In fact, BTG markets single-dose syringes of Delatestryl with 20 g. 1-1/2" needles. Go figure . . .
Obviously, I've since learned that 20 g. is neither necessary nor pleasant. For glute shots, I generally go with 22 g. 1-1/2" because they're more than adequate. For delt shots, 23 g. 1" needles - they're slower to push oil through, but a hell of a lot more comfortable. And quite frankly, I've started using the 25 g. needles for the quads. Again, slower, but a big difference in comfort.
So I've ended up using the 20 g. pins solely for drawing, then switching over to another pin for the shot. (Another reason to do this is that the drawing pin will dull somewhat from going through the rubber stopper on the vial.)
But if I were to buy another box of pins today (once I eventually use up the 20 g. box), I'd go with the 18 g. - no big whoop, but faster is faster, especially if I'm switching pins anyway.
As you might imagine, your 23 g. 1-1/2" needle will be slower for the glute shot, but still more comfortable than a larger gauge. So all in all, you've got a sensible plan. And since there's no rush to do an injection (at least there shouldn't be), go with whatg's comfortable.