X2 on Bumpy's slide out and I would add provisions for legs on the ground when extended for stability. You didn't mention a dorm-type refrigerator which many outdoor kitchens provide but with only 28" of head room your options for that are limited. Can you get your countertop and stove high enough to work comfortably? Maybe add some storage drawers underneath. Countertops are commonly 2 feet deep and you have a 4 foot width-two parallel slides or just one?
Two-sided hinged work surface(s) that sits over the stove and fold out-maybe split it into two surfaces that can flip out fore and aft (front and rear?) to allow two people to work. Put a sprayer on that sink faucet or maybe just use a small RV-type showerhead-good for all sorts of things- washing food, filling large pots, cleanup, keeping the cook cool :-) etc.
Just some thoughts, hope it helps.