Your washing machine and tumble dryer doors need to open in the opposite directions to each other, so if both are open, you can shovel wet stuff from one to the other efficiently.
Have a pulley maid to dry non tumble stuff hanging from the ceiling - our non tumble things dry overnight, it truly is a game changer.
Sink tap - get one of those flexible hoses so you can use it to wash off muddy boots, muddy veg straight in from the garen, stray guinea pigs, small dogs etc etc.
Tiled floor so you can mop down mud and detritus easily.
A tall cupboard space for mop, broom, ironing board and iron.
Normal cupboard and drawer space, this will be your random stuff drawer, and where things like batteries, matches, spare shoelaces etc will live. Cupboard space will be for your spare things e.g. hot water bottles, jams, hobby stuff (OH's cycling bits live in there where they are easy to grab, my soap making stuff has a cupboard to itself)
Don't forget to include plug sockets both at floor level and near your sink.
If you have underfloor heating, have it on a separate circuit to the kitchen, as the tumble dryer / WM may very well keep it warm enough. We have an upright freezer and the spare fridge in there and we don't use the underfloor heating there.
Enough coat pegs / shelves for hats, gloves, walking boots etc. A bench or something to sit on, whilst doing up laces etc is really useful.
Ours is possibly my favourite room in the house renovation / rebuild we just did. We did spend a lot of time thinking about our 'perfect' utility and what we wanted to do in it though.