If you are thinking about back inflate then why not a backplate and wing, better balance and you just need to change the wing if damaged or worn. With a simple hog harness you can have as many D-rings as you want, add pockets from OMS or DiveRite and it will even fit if your wetsuit shrinks :)
The best part and the reason your LDS don’t like them is you can mix brands and they will grow with your diving. A FredT backplate from online that you finish yourself, I have a 6# one for cold water and a plastic one from DSS for travel. Add a wing from anyone, DeepSea Supply (my Favorite), Hollis, DiveRite or whoever. Even LP has them! The harness is just a weightbelt strap or an old seatbelt if you would like it softer.
Ditto on the trim, don’t overinflate a back inflate, move your weights back and you won’t do a faceplant.