Absolutely no problem changing up the carpet. Things to watch for......make the transition in a doorway, an opening or along a visual break in the rooms (like the corners of the walls). I would stay in the same colour range, but just go to the other end of the spectrum rather than change the colour completely.....like light grey going to dark grey, not light grey going to navy blue. You want the separation but an easy transition on the eyes.

The timber island coming off the kitchen bench!

I think, like you said, due to the fact that there's a larger space when it comes to the hotel lobbies is the reason as to why it works. I think that no matter what you put on the walls (whether it be concrete or marble) will result in tiles not working out. The industrial look tends to be exposed brickwork anyway, or cream or white colours so maybe that's an option you could look into. What did you end up doing?

A very simple layout keeping the floor space within the kitchen, the WIP takes up a lot of space with not much gain, The broom cupboard could be moved to the Laundry/entrance, narrow. If the wall has been bumped out to the eaves on the deck side giving an extra 300 depth to the kitchen you could make the island 2700 x 1200 and all drawers. The wall of narrow pantry will hold all pantry needs and more, no deep cupboards to dig into. cheers