From what I can see, I agree with the others. This seems like a pretty good layout and if it's working for you, I don't see any reason to change it. The only thing I could see adding is a prep. sink by the window. My kitchen sink looks out over our patio/pool and I have to admit, it's really convenient to reach through the window and dump out a drink, or use the sink. That being said, we don't have a bar ledge, but instead have a counter-height patio table, which seems to work better. Instead of passing food through, and then walking around. I leave it on the counter, walk around, slide open the window, and grab it. The pass through is for just that, but when we're sitting outside, everyone has their back to the kitchen window and facing the pool, or watching the "Grill Master". Most of the homes around my area have ledges, but I have found that it's more, in the way, than useful, since we have to reach over the ledge and through the window, making the interior counters and sink, harder to access. The pass through window is actually 4' tall sliding doors. The benefit is that the window sil is completely flush, with the counter and pass through area, and both sashes, are moveable. As for your interior, the only think I might change, depending on what's on the other side, is instead of having the breakfast bar as it is, I would eliminate it and put one large island, with the cook top, that extends all the way to where the breakfast bar is now. The bar stools would wrap around the end, and one side, making for better conversation, as well.

my 8 seater table with chairs fits in 3300 x 2400 with the chairs pulled away from the table...Without walls closing in your dining room on two sides there should be enough space for your table and for someone to squeeze around to go to the bathroom but if you have 8 adults for meals regularly it might be necessary to consider a "bay window" style mini extension and rotate the table to extend out over the deck area with sliding doors and side windows it would have a conservatory feel with an overhead beam at the join and sloping ceiling in the extra space there would be no need to attempt to continue the original ceilings

I understand the beam being installed when you did your earlier extension as that was an external wall, that's why I have suggested keeping part of the wall next to the island which was also an external wall, to support this, I will check this in the drawing to ensure it lines up for you. By opening up this wall as much as possible you are allowing more light back into the house The cost of running plumbing across I think is negative/comparable to moving the plumbing for the re positioned laundry and kitchen and removing any load bearing walls. Storage in the new kitchen is a big 2900 x 900 island of drawers for easy access, I have added a wall oven but that could become a 600 pantry with drawers in the lower part with a shelf above for small appliances. The wall with the TV could be a wall of narrow built in storage to be used in any way you need. This floor plan gives better flow between kitchen/family.dining/alfresco and better for unloading the car with the driveway running down beside the kitchen and verandah

Exxy to move the stairs (but brilliant idea!) - so how about take out dining/hall wall and put just one long line of low kitchen cupboards down where that wall was or closer to the opposite side - so you open up all space and see all from walking in the front door. Make either a horse shoe kitchen config with cooker at top end. Then paint all cupboards in same colour - say a gum tree green - and give them new handles. In area between cupboards newly tile or lay a lino floor as easy and inexpensive to do and there are some really pretty decent patterns these days. If you've any money left over or later, boost the lighting with a strip of spots that point to the island worktop, the window worktop AND the cooker. But where is the fridge to go??