Ditto on the big mudroom. Some place for sports equipment (balls, shoes, helmets, pads...) I only have two kids but they're multi-sport, especially DS, so we have shoes for multiple sports, plus baseball bats, football pads and helmet (which get stinky) and myriad other stuff that ends up by the backdoor (in the mudroom.) (DS is 14 but already 6'4" so storing all those shoes is no small thing, pun intended.) Extra space in the garage for joggers and strollers when they're little, and for bikes and maybe golf clubs when they're bigger. Also a handy storage space (basement or garage) for holiday decorations. Seems like a small thing but at least in my neighborhood everyone has Christmas/ winter holiday lights; lots of Halloween decorations (kids love those); stuff for Easter, etc. (And room for yard work stuff like a lawn mower, hose reels, shovels, etc.) If you don't have one yet, you may end up with a pet so space for bowls, food, etc. (probably in the mudroom) will help. Ditto the idea of a powder room near the backdoor / family entrance. You don't want kids tromping through your house to use the restroom, and if you're like me you DO want to have lots of kids at your house so you know what they're up to. (I have teens.) If you like to have people over, it's nice to have easy access from the kitchen to the outside for grilling, outdoor happy hours, etc. Homework space is interesting, at least in my house. We have a 'home work room' with a printer and a desk for each kid. But DD prefers to do her homework at the kitchen counter which makes me a bit nuts because I'm constantly clearing away papers. She's in high school and they have a TON of books and papers. We have a finished basement, which is great for when one of the kids wants to hang out with friends or when they were younger and had sleep overs. It's also where I store craft stuff which we don't use so much anymore but did a ton when they were little. Somewhere on this board was a thread of 'what would you do differently' that might help with ideas. And for whatever it's worth... we use our warming drawer in the kitchen all the time. As the kids get older their schedules can be all over the place, especially if they're in sports. We try to always have a family dinner, but sometimes end up with DS's plate in the warming drawer if he has a long/late practice. We also use if for pizza nights, happy hours, holiday dinners, etc., so I don't consider it an 'extra' - I use mine often.

You could probably do 1/2 or 3/4 wall of glass, like a shower screen, attached at the floor and wall. Frosted like lazygardens suggested. Here is a link that might be useful:

I'd still have something on the bedroom windows in order to make it sure the room was dark at night, and to provide a level of dimness during the day if I wanted to take a nap. It might be a room-darkening roller blind that would pretty much disappear when it was up, but there'd be something on the window. Any first floor bedrooms or bathrooms would also have something to provide privacy. Even if random passers by aren't able to look in those windows, family members who are outside might be able to. My cousin's first floor bathroom has nothing on the windows and I've checked and you can get an eyeful if you are in the right place in the back yard at the wrong time. It doesn't bother her family, but it does bother me. Other rooms might need something for light control during the day--a TV room might need something over the windows to control glare. A large room with high ceilings and a hard surface floor might need more fabric in the room to prevent an echo-y feeling and window treatments would help with that. And there's the fact that the right window treatments can aid in keeping the house cooler in the summer and warmer in the winter, helping to save energy and reducing energy costs. So I guess for me, window treatments where they aren't needed for privacy would be on a case by case basis, because there are reasons other than privacy to need something on your windows.

Miscanthus sinensis 'Gracillimus' specifically goes well with Hydrangea macrophylla. Because of the contrast in structure between the two. I wouldn't see Hydrangea paniculata being as effective in combination with a Miscanthus variety that flowered conspicuously because of the general similarity in shape of the inflorescence of each. A good balance in a planting featuring plants that flower together is half of them with spike shaped flowers and half with rounded.