"I hate the dead space between my stairs and the wall."

Tell your architect again, stand firm, and be prepared for a reworking of everything. But anything can be done.

If you want crowd sourcing of ideas, post a floor plan and front elevation.

If you have a U shaped staircase, there is going to be space in the middle. What is under the stairs and upper landing?

The stairs also pass oddly in front of the windows.

You could avoid the space in the middle with a higher intermediate landing and switchback stairs but that would require a longer run of stairs between it and the first floor.

(You didn’t ask, but the door at the top of the stairs: would the room still work if the door were hinged on the right instead of the left?)

From what i can tell from the 3d (which isnt much at all), if you get rid of it, it would result in a vwry circuitous stairs. Enter facing the wall, up mayve two steps to a landing, turn 90*, then up a few more steps to a wide landing, turn right 90* and walk the landing, then turn left 90*, and up the remainder of the stairs as drawn. phew dont know that i would want that.

They have to occupy a certain amount of run because of the rise needed. Reduce the rise, and reduce the run. If you want better designed stairs, lower the height difference between floors and go for a traditional switchback with an intermediate landing. The thing you don’t like about these is caused because of the design program and overheight measurement between floors.

I would put a stunning, very large original painting or hanging there. Or mural. Or grandfather clock. Or tall sculpture.