I guess it sounds interesting. I don't use traditional sanding blocks that much since the integrated 3M abrasive sponge things are so cheap and my power contour sanders can be shaped to just about anything.
The sanding blocks that use 3x21 sanding belts are handy for coarse to medium sanding by switching grit size belts. The simplest ones are just made from a block of scrap wood but commercial versions have more edge profiles. http://woodworker.com/fullpres.asp?P...3&LARGEVIEW=ON