When I went house hunting there seemed to be quite a few housed outside, one would hope in winter they will be running so will not freeze, but I am a little worried that one would in error of course run out of oil, so it can freeze.
You can get trace heating to put on the pipes, which means even if for some reason the boiler can't run, nothing will freeze, but I would be rather careful to ensure it is protected from the elements, and of course provision so if it does break down, it can be repaired, no repair man wants to dig out the boiler from the snow, so if not easy to repair, unless you have a contract, you may find the repair guy leaves you until last, or gives excuses why he can't get there.
I must admit we do tend to put things in the kitchen which should not really be there.
I know first house we would pull the twin tub washing machine to centre of floor and washing day there would be cloths all around the kitchen as they took their turn in the washing machine before being hung out in the car port. And clearly no cooking was done while doing the washing.
But today with front loading washing machines and driers there is no reason why they should be in the kitchen, dirty cloths and food does not really mix.
The same applies to domestic hot water, in the days when the boiler was part of the solid fuel cooker, there was no option, the boiler had to be in the kitchen, with wall mounted gas not so much a problem, but floor mounted oil does take up a lot of room.
Mine is in the back kitchen, but I hardly every use the back kitchen, except for BBQ's, the front one is normal one we use. But room is a problem, at moment my wife's e-bike is in the lower floor bath.
OK my house has three floors, so can find room for the boiler, but when moving outside it would make sense to house in some thing like a shed or garage, this allows room for maintenance, and maybe can also house other items which should not really be in a kitchen, like the washing machine.
Since we moved here after my mother died, we ended up with two washing machines and a tumble drier, one pair is in the utility room, and washer drier downstairs with the boiler and only used for my overalls.
If your going to have water and electric outside with boiler, why not also have washing machine and drier outside as well, in an out house or shed.
Back in the 30's this was common, the 2 up 2 down houses would have a yard with a row of out houses, the last one would be the toilet with the hatch on the back ally so the muck cart could empty it. The coal would go in another, and often there was a wash house as well, where the tin bath was hung up.