I'd love to see a mechanism for using RLE encoded ISOs for compression. Would work well for shrinking dummy files as well as being extremely fast and easy to do.
Like CSO it would be done on a sector by sector basis with a header for uncompressed sectors.
Would also make doing compressed dumps on the PSP itself somewhat more bearable, since RLE encoding doesn't require much CPU time compared to ZLib compression.
Edit: Sorry wrong forum, this should be in speculation! Mod can move it please?