Waterfall counters IMHO only work in really contemporary kitchens and the fabricator needs to be perfect with matching grain in the granite or it fools no one .. I also do not like the the 2 thicknesses it ruins the illusion. A nice simple eased edge on a 3cm slab is timeless and suits all styles

I assume that the dishwasher faces towards the perimeter cabinets = you don't see it when looking into the kitchen? If so, I have seen where someone did a thicker miter on the front with waterfall countertops on the sides (her kitchen is modern with flat panel cabinets) with a shorter miter along the run where the dishwasher was located. You didn't really notice it - the perimeter countertop wasn't a thick miter either = the dw side of the island worked with the range wall of the perimeter cabinets.

It is difficult to provide an answer when there is no other information re: your kitchen layout/design.

You assumed correct. Range and fridge side counter will be 1 1/4. Island facing this ie dw side would also be 1 1/4. However island side facing family room using 2 1/2 or something thicker. And yes modern with flat cabinets.

We have a waterfall on our island with Blue Pearl granite. It has an eased edge on the top. Looks great. Our cabinets are also modern/flat.

It looks fine in my friend's kitchen - I've seen many islands with thicker mitered countertops vs. perimeter countertops. Due to the dishwasher run being on the hidden side of the island, it will simply look as if your island has a thicker countertop. I don't think that I would have noticed my friend's island countertop - she pointed it out to me and asked me what I thought.

is the waterfall edge seen from the family room? or the whole island?

A build up edge just makes the counter higher. Not sure why you can't do that because of the DW? Instead of having a 35 3/4 +- height , the top of the counter will be 37" +-. The space under the countertop is still 34 1/2 which is standard cabinet height.

Am I missing something?

Good luck

The granite people must be jumping for joy. "Hooray! We have convinced another one that they just gotta spend even more."

@Debbi Washburn - I was wondering the same thing as you've asked in your post when I initially read it. However, I then assumed that the OP didn't want to have the island be taller than the perimeter cabinets.

My friend thought that she would notice the different heights and that it would bother her. Since she also has waterfalls on both sides, it allowed the shorter miter over the DW to be "hidden" while keeping the island and perimeter counters all the same height.

Obviously, if OP is okay with a higher island, all that needs to be done is something like this:

I should have asked the OP rather than just assuming!

Appreciate everyone’s comments. Floors are Concrete radiant and some concern that they’re not perfectly level which would affect some of the height and install. Will review ideas with contractor