Sorry, you need to have a disc drive connected for the system to work. The drive doesn't need to work so long as it is properly connected.
Even SNEEK/UNEEK/neek2o and any other type of EmuNAND still need the disc drive to be connected, they merely bypass the NAND. The difference is basic EmuNAND (such as that used by USB Loader GX) will redirect NAND access (ie game saves and such) while SNEEK will do that as well as redirecting calls made to the disc drive. Your disc drive is still required several processes run by the system.
Example to help explain further: SNEEK cannot redirect a call made to the disc drive if the disc drive is not connected, the reason being nothing can call upon the drive if its not connected.