Your lay-out looks fine. A consideration however is pipe lay-out to the house fixtures. Keep in mind that the cross sectional area of 1/2, 3/4 & 1" pipe is .19, .44 & .77 sq in. Those numbers equate to vol of water to be moved before delivery of hot. In some situations I've run a dedicated 1/2" pipe to the kitchen so I basically by-passed the main 3/4" trunk. My point is to look at your water heater placement as a component in your "system". Where is the best location for the water heater for your on-going comfort and conservation of both energy and water. Don't be afraid to move the water heater upstairs if you can vent it and it improves the system. I would strongly suggest as you develop your finished basement spaces that you not Sheetrock the ceiling. That basement ceiling is your mechanical area. Put in a drop ceiling. You will still be able to access everything. I am having this issue at my daughters house. The PO rocked the basement and garage and I now have to trash all of it. Oh, one other thing. Install a 3/4" pex recirc line. You may not need/use it, but if you decide to it is there. Easy money when it is open. Not so when done. Your plumber will likely suggest 1/2", but depending upon the recirc system you install you will have much better operation with the 3/4".

"Yeah, the cover plate has to be pushed against the cables and the tension of the cables actually tweaks the main breaker enough to keep it from fitting into the opening in the cover plate without some manipulation. " Wire dress is not correct. Form and trim to lay against the inside BACK of the panel. Panels with feeds not at the back quickly turn into a PITA to to route branch circuit conductors. There always seems to be a feed in the way. It can take some force to form larger conductors, and 'tight laid' 4/0 aluminum is a real chore (the wire was run through a forming die to make it more circular before jacketing, leaving the individual conductors distorted so they cannot slide as easily across each other as the cable is bent. If you look at the end of a cleanly cut cable you will notice all the flat spots between the wires. The individual conductors are spiral laid to make forming easier, the tight packaging makes them stiffer.

Thanks for your comments. Your response made me realize I neglected to mention an important fact in the first post. I'm replacing a small (6') v-shaped island that had sink and dishwasher. The large (13')new island will go over the existing floor drain. Water and electricity to the current island come from above via an awkward looking pillar attached to the end of the small island. So I do have drain infrastructure in place. Only need to bring in water, gas and electricity from below. New island will not (and cannot easily) "touch" the existing pillar to get utilities. Based on the earlier comments, would it be desirable to use the existing drain "portal" through the slab? e.g. expand the hole at this location to accommodate the other services. From everyone's earlier comments, it sounds like a very good thing to drill where you know (with certainty) there are no cables. Any additional comments/advice will be welcome. Thanks again for all your help. Feel like I may have dodged a very painful bullet by not trenching as recommmended...

You've lost me. I don't see two circuits in your description. If you're asking, can you run all your receptacles back to some common point rather than daisy chaining them along, the answer is yes. However, you need to make sure you don't overfill the box capacity of the box you're using as the source point (talk about cramped boxes).