much - That's an interesting question about prioritisation. I am trying to remember how we made decisions. I think a lot of it was about storage, really. We didn't just want extra space, we wanted to design a house that would basically tidy itself by creating a designated space for all of the things we own. But it's not really just about a space, but about a flow. So we made a list of the routines that currently go 'wrong'. For instances, we get important bills, documents etc through the post, and what happens to them? Currently, they tend to get dumped in an untidy pile on the stairs, or worse, in the kitchen. But what if they got opened in a space where everything was available to file them or process them immediately? So we are building a small fold-down desk in a cupboard, and creating a shelf above for all our paperwork, so we can process it all straight away.
Similarly, we had a conflict between needing more guest space and more study space (DH and I occasionally write together, so we'd like a space that isn't the dining room table where we could work together). So we have created a hybrid room. We are making a 3 metre long desk with two chairs. But it is hinged, so the middle section folds against a wall and becomes a headboard when we need the space for additional guests. We've found a bed that can be assembled really quickly that will fit in the gap, and a folding mattress. This means we will have 2 guest rooms, rather than our current one, so we will be able to host 4 people without having to put guests on uncomfortable sofas! You get the idea! Basically, we made a huge list of "dysfunctional spaces in our life" and tried to solve it!!
For utility - if laundry is the priority, you can literally have a very effective workhorse of a space in something cupboard sized. A washer, a dryer, and a couple of hampers for laundry don't require much space. In terms of putting away, what is the precise nature of the problem you're encountering? Could it be that there is a knock-on issue that clothes are difficult to put away because there's not enough storage for them, so people in the household avoid this? Or is it a problem of routines - that one person is left to do the entire household's folding and putting away, and they are getting a bit overwhelmed?
Study & noise - it depends on the person and the nature of the work being done. If it is highly complex and requires absolute focus, like working on theoretical physics or something, an open layout might not work. If it involves confidential material, it might not work. If it's doing a job that's normally done in an open plan space anyway, however, then it might not be an issue at all, and could even be a bonus - working from home can be a bit lonely!