I've made several denim quilts with no batting. They are a nice weight & not overly heavy to sleep under. Your bedspread would be heavy overall just due to the size you are making it. That's not a problem, but it can be a little awkward toward the end of the sewing process.
Your construction method makes sense to me, but for something this big I would do it in 4 or more sections then sew them together, rather than doing it a few rows at a time. I think doing by it that way it will be easier toward the end so you won't be sewing a few rows onto the majority of the completed quilt/bedspread. My only other thought would be to make your original circles big, like 12-15", but you can play around with that to see what size you like best.