I have seen several outdoor kitchens made of stone/fancy SS BBQ cabinets etc. If that look is ok it seems better than wood.
I did build one outdoor kitchen on a deck by the ocean, based on customer specs and some of my own input. Make sure you exclude finishes and adhesives and whatever you can think of from the warranty.
the one i did do was DragonPly boxes and drawer bottoms, sapele five piece doors/panels, panel edges sealed with west system and bottom rails drilled through in several places for drainage. I used spaceballs also, which is the only time i've really used them. Sagatsune ss hardware was used for slides and hinges since that was all i could find for euro style hinges in ss. The hardware is 304 not 316 but there has been no corrosion despite being within 100' of the ocean. All ss fasteners and west system adhesive. Everything has held up over about 5 years pretty well, one door warped slightly. I did re-adjust everything a couple of times, but eventually realized it was the deck itself moving beneath it quite a lot told the owners i was happy to come once a year and adjust for a fee after year 3. At one point before the stone counter was installed i was on site and the owners had removed the temp covering prior to a storm - all the drawers were full to the brim with water, but everything still works fine.
I have had to go back three times to replace hinges that were almost torn off due to wind on the doors - another issue i warned about. After the replacing two sets gratis as a courtesy, i charged for the third and upon returning yet again to see the finish failure i noted some pretty hideous catches on all the doors.
At the time i convinced the customer to leave the kitchen raw, but they eventually were insistent on finish. Since i have never seen a finish that lasts outdoors like that i demurred. They had a 'professional' do a clearcoat and in less than a year it has failed. They called me for further recommendations and i basically had to give a courteous shrug. When they told me they were having it done i reminded them why i recommended not doing any finish and that i expected it to last less than a year. Here on the coast there is a not small industry of boat vanquishers who seem to go in circles re-stripping and re-varnishing all sorts of marine woodwork. If there were a solution those dudes would know and use it.
Making sure the customer has realistic expectations and understands the realities of wood/ground movement, sun/weather exposure, wind etc is important - which is why i recommend the Stainless Steel prefab idea. Even better on individual rolling carts.
If i were do try it again i would take a serious look at Richlite or a corian like product for doors/panels. My experience with Extira makes me think it would not be a great kitchen product. Im not sure how to deal with the ground/deck movement issue.