I could definitely use a louder alarm, or a vibration alarm. Just something remotely practical.
LED backlight would be sweet.
But honestly, I'm pretty happy as is. Just minor quibbles.
I'd love to see Casio come out with different bezel shapes, that still fit the existing case. Maybe one that's chunkier with more resin to protect the crystal. Beast mode!!!
Maybe new and improved nylon bull bars that don't have paint chipping issues.
Better looking strap adapters would be cool.
I'd even dig new resin straps that looked more like the old DW-5600C straps.