I'm a very, very novice quilter (I made one quilt 30+ years ago) but an experienced seamstress. So I think the following would work but have not tested it and really don't have enough quilting experience to spot obvious flaws.

As I understand it, rag quilts are made by cutting fairly large patches, using half inch seam allowances and assembling the quilt with the seam allowances facing out. Then the seam allowances are clipped every quarter to one half inch perpendicular to the seam. When put through the washer and dryer, the short clipped threads come out of the seam allowances, leaving half the threads to form a thick fuzzy, raggedy edge around each patch. Essentially, you're losing half the thread from each seam allowance.

Then I remembered that about fifteen years ago, faux chenille was all the rage in the garment sewing world. It was done by layering 4+ fabrics, quilting them by machine on the bias, slashing all but the foundation layer between the quilted lines, then putting them through the washing machine. Most of the time, the fabrics bloomed beautifully, forming thick, luxuriant lines of frayed threads all over the garment (occasionally there were failures that just would not bloom). I made a vest and two lap blankets this way and it was great! I used rayon fabrics for my vest sandwich and people literally could not keep from petting my shoulders and back just to feel that wonderful furry, silky texture when I wore that vest. Heck, I could hardly stop petting myself. LOL!

So then I thought: why not do this for a rag quilt? Cut square patches, say 5 inches, on the *bias*. In other words, deliberate cut the squares so that every edge is a bias edge. Sew the patches with a half inch seam allowance, so that the finished size in my example would be 4 inches. I'd be tempted to use two or three layers of fabric sewn as one and skip batting, just have a backing. If different colours of fabric are used for each layer, the resulting fringe will be multi-coloured. I'd outline quilt an eighth or a quarter inch from each seam line and maybe a big X through each patch, just to keep it reasonably stable and in position.

The advantages would be that since all the threads stay attached to the seam, the seam allowances form really thick, furry lines; plus, it would eliminate the nontrivial task of clipping the seam allowances.

The drawback would be that the edges of the patches could be quite stretchy, particularly if done in flannel or denim. Dealing with all those bias edges could drive one batty(er).

I think this disadvantage could be taken care of by starching the bejeebers out of the fabric before cutting it. I'd actually starch it with a medium thick starch two or three times, until the fabric felt as stiff as cardstock. The starch would act as a wash-out glue, holding the individual warp and weft threads in position until the whole thing went into the washing machine.

If it was heavily starched, it might take a couple trips through the washer and dryer to completely wash out. But rag quilts usually do need a couple full wash/dry cycles to reach their full shaggy glory.

I hope someone adventurous will try this!

PS-drawing on my experience with faux chenille, make at least one test square first. Very occasionally, one or more fabrics don't bloom well (I suspect that some of them may have been treated for wrinkle resistance). You can do it with one 5 inch patch from each of your proposed fabrics. Sew one half inch from the perimeter plus an X through the middle, then throw it in the washer and dryer a few times. I'd actually make a couple different experimental sandwiches, in order to play with the order of the layers. Once they've had a chance to bloom, see which one you like most.

PPS--Obviously, ravel-prone fabrics are most likely to succeed at this. An all silk layer sandwich would give an incredibly wonderful texture... but at a price that is beyond my pocketbook, alas.