I'm looking at this problem too, all I find is WPA info... nothing about WEP. I'll keep you posted if I find anything.
/usr/bin/uaputl sys_cfg_wep_key --help
..
/usr/bin/uaputl sys_cfg_protocol --help
Usage : sys_cfg_protocol [PROTOCOL]
Options: PROTOCOL: 1 - No RSN
2 - WEP Static
8 - WPA
32 - WPA2
40 - WPA2 Mixed
empty - Get current protocol