This is one of the more bizarre arrangements that I've seen... Not sure how the interior space lays out, but I'd consider closing in some of that window area with wall space. Finished attics are generally difficult to heat/cool, so reducing the window area would help that out in addition to providing a more conventional appearance.

Depending on what the room(s) inside look like that have those windows maybe something like this? You could add shake siding around the windows there.

How big is each casement window pair? Are they easy to get to for opening or are they fairly inaccessible?

@HomeSealed Exteriors, LLC Who/what type of business would we hire to help with a vision of what it could look like? The window companies don't really do design work, and it seems outside of the purview of our go-to contractor. I've been unable to find an exterior designer willing to consult on just the windows (without purchasing an entire package for whole front of house). Thank you! @apple_pie_order Right now, they are inaccessible (there is a piece of glass on inside that cannot be opened). Height-wise, they are very accessible and are located in the upstairs bedrooms at average window height. Is that what you mean? Thanks for weighing in!

Your best bet is probably to get ideas from some of the design crowd here on Houzz who generously offer their time and talent to help, or hiring a general designer that is willing to take on a smaller project like that. Ultimately that will be the best route as if you are making these modifications, you'll need to submit plans for approval to your local building dept anyway.

There are some exterior remodeling companies that will do more design than others, but most that are dedicated just to windows and doors won't.

Thanks for info. Since they'd be accessible if the piece of glass weren't there, I suggest you get casement windows that swing out. With any luck, they'll be a standard size. Also consider safety egress requirements for the upstairs bedrooms- if you need to get out in a fire, the rules are designed so you have big enough windows at the right height range from the floor.

Casement windows will probably look like they belong to the house design. Awning windows aren't used in my area much, but it's possible they are used in your area. Take a drive with google streetview or walk around on foot to see what types of windows are used in your neighborhood.

I kind of like them and would look to just replace them with same, but modern double pane and functional.