Haven't RTFT -- though close.
Underfloor heating in any room without wall-to-wall carpet; cheap, more eco, and lovely and warm. In bathrooms ALSO have heated towel rails.
YY to multiple electric sockets everywhere. Don't forget the bathrooms -- before you know it you have three electric toothbrushes plus two electric razors sharing one bathroom all needing to charge.
While we're on it, if you or anyone you know might EVER need a hair dryer or curling iron or straightener, make sure you have outlets near a good mirror.
Full-length mirrors near every closet, and by the door you use most often.
More bathroom tips: put the loo flush directly behind where the seat goes up so men are forced to put the lid down! If you have a shower in the bath, still have panels instead of a curtain, and try to get the shower head put on the opposite side from the drain so you're not standing on the drain to shower.
For general ideas, look at public bathrooms in places like hotels -- ideally, yes, you'd have the counter be one with the sink or at least have the sink underslung: you DO need a counter around the sink even if you also have a cabinet because you have to put things like makeup remover or toothbrushes down briefly no matter what. And for goodness' sake have the cabinet flush to the wall, not projecting out like those annoying little glass trays I always hit my head on. Similarly, in showers, build a large nook for bottles etc but at shoulder height above the splash level so they don't continually fill with water.
If it's a stand-alone shower, make it large off-white matte ceramic tiles that neither stain nor require re-sealing. And make the shower tray a single custom-made ceramic piece -- not at all expensive. Either way at least one shower head in each shower comes off its bar so you can wash off cleaning products easily.
Kitchens: a stainless steel sink large enough for your largest oven baking tray. Or better still, American-style, two side by side -- at the very least the second is good for putting in the dish drainer which you will need even with a dishwasher, because some things always end up being hand washed. And the sinks are of course (like bathroom sinks) underslung from the counter so the counter runs right up to the sink edge. The tap in the kitchen has a spray option. Do NOT have grooves cut into the counter, they don't help drain water but just accumulate grunge.
But an appliance garage for things like kettles and toasters is great. At the least zone common activities like tea-making so tea leaves and coffee beans, kettle, cups, sugar etc are all in same place. Same for breakfast stuff -- toast, tea, cereal...
Dimmer switches in every single room. Especially including bathrooms -- nothing more relaxing than a bath in a half-lit glowing bathroom.
If you live in a hard water area, a water softener before the boiler will save you a fortune on the life of all appliances as well as a lot of cleaning. You can still have a tap with hard water in the kitchen -- it does taste better.
I once found a rather extreme and rather out of date book by an American professional cleaner called Don Aslett called "Make Your House Do the Housework" and I strongly recommend it!