Siding. Stone and brick do not normally play well together. This was a happy coincidence.

Pewter Gray Horizontal Clapboard. I would do an 8" tall. Also in my mind you got a break that the brick is backorder as i do not like a façade with both brick and stone.

PS take a close up of the stone in bright light, if you want color help

When taking another picture, put a sample board next to it of the siding choices you have. The builder must have given you a brand and product line to choose from? Bonus if you have a roofing shingle to include in the picture.

I agree with everyone else that brick and stone are not good together. Hardiboard has several beautiful options, board and batten, clapboard siding, or shingles. I would consider board and batten on the two front facades next to the stonework.

Brick, but only if you are going to remove the stone and replace with brick.

"Our brick choice has been delayed twice."

Divine intervention.

Is your foundation wall detailed with a brick ledge for a full brick veneer?

Yes it is

Depending how it's detailed (flush with sill plate, notched below sill) and if the wall sheathing sits proud if a notch, you may have to have a metal flashing made. IMO deal killer aesthetically right there (I think the whole house is brick?).

I would go with board and batten. You can still use brick for the bottom, when it becomes available or use the stone.

Why not just keep going with the stone? It sure looks more like brick than stone. What color brick are you waiting on? I agree with the likelihood that the brick and stone will not work together nicely. I would go with hardy siding that matches the lightest color in the current 'stone'.