Info re bleach:
I have played with bleach to remove dye from some of my batik fabrics for both blocks 16 and 5, and I have been having discussions on my PDA about how I did it, and what I used. In one instance, I used domestic bleach that is available here in a gloopy thickened state but doesn't seem to be familiar to US quilters. We have now had Dishwasher Gel suggested as a suitable alternative.
I have also read up some more and it seems to be generally advised to use a product called Bleach Stop after washing the fabric. In Europe an alternative to that is Hydrogen Peroxide (3%) Both would neutralise the bleach.
The other product I used (on block 5) was a Bleach Pen - it isn't so easy to control because of the point on the pen (not particularly fine) but some interesting results can be obtained with a bit of experimentation.
Again, with the start date not being until June, you all have some time to play with these, but please take care when using them and follow instructions on the various products.