I like ensuites, why do you want to share a bathroom with anyone other than your spouse?
Even young children benefit from having a bathroom each, they have their own products, potty training seat and steps, own towels, toothbrush etc. You teach them how to keep their own bathroom clean, hang up towel, wipe sink. As they get older they clean their own loo and shower, as teens they have privacy eg girls starting peroids have a private bin to put used pads/tampons in. Boys can set up their shaving stuff etc.. and nobody fights over who used/moved their things or made a puddle on floor or forgot to replenish loo roll.
And nobody has to queue or use a smelly one. Saves so many arguments between children as well as teaching them to look after own space. They can go to loo in night without creeping down a dark landing trying not to disturb others. More hygenic as bugs like norovirus easier to contain. Skin infections or fungus/cold sore virus/bacteria don't spread between towels being shared or touching. I hate bathtowels all being squashed together, or having to take child seats on and off toilets, it's outdated and primitive! And I can't imagine guests sharing the family bathroom, awkward and grotty for everyone. The days of queuing for shower in my dressing gown are long gone.
Currently we have a dressing room between our master bedroom and bathroom, giving privacy and space. Windows and extractor fans in all ensuites. Guest ensuite needs updating but is functional, with space for them to leave their stuff on shelf and in drawers. I keep it set up with a basket of spare toiletries and sets of towels. Currently both children share a large bathroom, but we plan to convert garage soon, as ages and gender mean they have different needs, products, want to use it at same time, use the wrong age toothpaste etc.
If you have a huge family bathroom with 2 sinks, multiple shelves, space for everyone to have a basket of stuff maybe it's easier.
My ideal house would be an ensuite per bedroom, plus a large family bathroom downstairs with a double shower, large spa type bath and storage space for all re-fills, cleaning caddy.
I find it easier to keep several bathrooms clean as you set aside an hour then go from one to another with steam mop, steam hose attachment, bleach, soap refills etc for deep cleaning. And a daily wipe down to reset and tidy, change towels and mats, remind older children/teens of chores. The same as going from bedroom to bedroom changing sheets, dusting, organising, delegating jobs.
An extra downstairs loo or spa bathroom means couples have the option of privacy too, or someone can have a long soak in the bath. Nowadays I think baths are less fashionable, one per house is enough as people don't have time for regular baths. It's quicker and uses less water to shower before work/school. And easier to clean, less damp. We only have one bath in our house, and 3 shower rooms.
I agree with your architect!
Home office is awkward within a bedroom and home working not as common now.
We have a small office/study downstairs, which doubles as a gaming room and man cave. I wouldn't want anyone gaming or playing VR upstairs when children are asleep or I'm trying to relax in bed.
You could add a small office to the lounge or dining room. If one bedroom is downstairs then it's ideal to have guest bedroom and ensuite downstairs, so it's closer to front door and guests don't need to go upstairs, giving everyone extra privacy.
I know many families who have converted garage into a guest ensuite, that doubles as a playroom or office or gym or gaming room between guests. Keep it multipurpose.
Lots of families have adult children living at home, sometimes with partners staying over or moving in.
Our old house had a big ensuite in nursery, which was great when firstborn was a baby as I had a big room to keep changing table, nappies, nappy bin, all the stuff that comes with a baby.
People can always convert an ensuite into an office or storage room or wardrobe, but it's much harder trying to add plumbing.