Well, I finally got it figured out. Taken me a heck of long time, as I'd never set up a cross-compiled environment before, so I had no idea what was correct. Also, since shfs requires a kernel module, I had more problems there. It isn't enough to simply point at the Sharp kernel source, turns out I had to select the correct config file from def-configs, and build a module set before I could get it to compile correctly.
In any event, now I have it working, I've built a package. Keep in mind this will probably only work on the SL-6000L, and even then likely only on the stock ROM due to the kernel module. I've tested the package on my Z, and it installs/uninstalls cleanly, but I have no other hardware / configurations to test it on. Use at own risk...
http://files.tokomak.net/zaurus/shfs_0.35_...harprom_arm.ipkPlease report back any problems / other working configs.