am assuming this is a concrete structure, when shifting service toilet to utility area, and if there are apartments above, then running extra lengths of supply/drainage lines & introducing a structural sink slab (if this is concrete) under the new location can be charged extra.. it will be easier to divide the 3rd toilet. all services will be already available. only, do check on supply & drain pipes capacity as load is increased on the same pipes which were serving one toilet earlier..

Usually when you get side panels you automatically have space on the sides. If you have a full depth cabinet on the top, you automatically have space at the top and in most cases you will have leave at least 1 inch of extra room for the back of the refrigerator, so there is always air circulation since everything is enclosed. In the 70's they use to make a small recessed space behind like Fred said, today you don't have to do that, most Ref have flat backs, recessed wiring, not to mention the supply for ice-maker also comes in a flush mounting kits for the wall... so pretty much everything is recessed and only space you need is for air circulation and 1" is more then enough. In addition, if you make recessed area now and you push ref to far you will never get your doors open so doing all that is a waste of time, in addition most manufacturers starting to make 30" side panels.

I would not have a partition. It is just one more thing to clean, and adds a sense of clutter to the open space. I'd arrange sofa to face away from the kitchen, though. The sofa will then be facing the terrace garden, too.

Jey, Are you sure you don't want to leave any space next to the chimney. It will void your product warranty and you may find it tough while servicing it. One must leave 4-5 inches space for servicing and air circulation. Thanks. Nitin Cornerstone Designs, Bangalore.