I like the idea of using metric, but US appliances don't come in metric sizes. So your range and dishwasher cutouts need to be in inches and probably the refrigerator and over the range microwave.
I'm using Blum hinges, so the front row of 5mm holes will be 32mm system, but my cabinet outer dimensions will be in inches.
You might be able to get away will 100% metric if you used all imported appliances, but that is impractical and too expensive for me.