givio

Yes, I think it will work fine. You just need to think through what to do first. :-)

Like some other comments, I had a similar item when young. We called it a bedspread. The quilted, thicker part, lay just over the top of the bed, while there were two sides, and a foot end that fell down nearly to the floor. The head of the bedspread just covered the mattress at the head, and the bedspread there was covered over with the pillows, which laid next to the wooden headboard of the bed. Quite often these bedspreads were used on beds that didn't have a footboard (called Hollywood beds). My bed did have a footboard, but it had room between the mattress and the footboard that allowed a place for the bedspread to drape down. Mine was not gathered, and the sides and foot that dropped to the floor were not lined. The single thickness of fabric was a heavier weight though than quilting cotton, something more like a textured linen.

Actually, you can find antique quilts made in this manner-- the main part that fits the top of the bed, with three rectangles attached around the outer edge for the drop over the bed to the floor.

You could box the corners, like making a huge tote bag corner, by sewing diagonally.

I don't see a problem with putting wadding just in one area, so long as the edge where it is enclosed is secure, to stop the wadding from moving out. If your sides that drop down are lined, it seems that would be fine. I've made plenty of baby blankets (often named a 'receiving blanket') that are light weight with only a pieced top and a cotton or flannel back, and I imagine your sides that drop down would be similar. If you prewash/shrink your all your fabrics, I think you may have a better overall success with your idea. I'd suggest prewashing/shrinking your wadding as well.

Best wishes for a fun time on Quilting Board! :-)