Would it be weird to build a cloakroom with the washing machine/boiler inside?

[BingBo]

We have hard time to put the washing machine in the kitchen (not enough space for all appliance!).

Would it be weird to build the cloakroom big enough to have the washing machine and boiler inside?

Ideas are welcome!

Not weird at all, OP.

In the US it's normal to have a basement for the washing machine, or failing that it'd be in a bathroom in a cupboard, along with dirty laundry hampers (so you undress before your shower and deal with your dirty clothes then and there.)

Same in the Middle East. Washing machine in or near to bathroom, definitely not in the kitchen.

In Japan the washing machine was in the bathroom too, although other people had theirs in the veranda or balcony, or outside their front doors!

In the UK from what I've seen it appears to be the norm to bring your dirty clothes into the kitchen to clean them. So people's opinions on this will vary depending on what they're used to/ where they're from.

People concerned with peeing next to a washing machine - lol!

OP, it'd work nicely. Get a custom built cupboard to hide it all in. Put the drier on top of the washer top save space. If you have Pinterest, search for "bathroom utility room combo" or similar to get some ideas.

I've got my washer and drier in the downstairs loo. The room is about 2m x 2m and they are along the back wall under a little window with a nice worktop over them. The sink and loo are on the left wall and on the right I have a duotherm radiator so I can run it on electric on a wet summers day rather than on the central heating to dry stuff.
It works well, the loo seat is convenient to sit on while filling the machines 😉
Then everything is nicely boxed in, painted and mosaic tiled. I was contemplating a covering to go over the appliances but looks absolutely fine.
It means I can shut the door on it all and not hear them spinning. It's an efficient use of space and all the plumbing was already there.