I would think building anything involving cutting into camper walls would be cost prohibitive.
If you really want an outside kitchen, there are many makes of TT that have them-buy one of those models.
Or....do a few mods and make one yourself.
But since you already have an outside fridge, it should be easy to hookup an outside combo grill/stove to your quick connect gas line, and if you have an outside shower tap ( or even if you don't) getting water to the area is pretty easy. You can attach a small table to the side of your TT.
We have done all of this with our TT. Got brackets to attach a 4foot table to the TT. We have the Louis & Clark outdoor portable kitchen and connected it to the outside shower, so we have a sink with hot or cold water. Also have Coleman LXE grill and just learned how to hook it up with TT quick connect. We don't have any outside fridge, but we don't feel we need one. All this fits under the awning on the back 1/2 of the TT.