Hi @Nezz,
Welcome to the Bunnings Workshop community, it is wonderful to have you with us.
I can't say I have seen it done; however, I can't see any reason it wouldn't be possible if you could find an outdoor-rated dishwasher that would fit into either the AlfrescoPlus 550mm Single Fridge Module or AlfrescoPlus 960mm Double Fridge Module, and it was close enough to the necessary plumbing and electrical outlets. They are essentially just appliance compartments, so as long as the dishwasher will fit in them and is suitable for outdoor use, it should work.
Let me know what you think.
Jacob
