I love Billy bookcases! I have two, with solid lower doors in my office (filled with genealogy notebooks and other stuff) and have just bought one with full doors (top glass) for the guest room to store my fabric in. I have it in place (sans doors yet) and have been folding my fabric onto comic boards; hope to finish today. Not sure it will solve all my stash issues but will certainly help!
If I had the space, I'd copy your Billy bookcase scheme. Love all that shelf room!