I haven't personally tried it but it should work. The Mifi router should not be able to distinguish between another router or a PC both are clients to the Mifi router. You can use the firmware posted in that thread or use a wireless client adapter like this one
Before spending the money on a 4G adapter make sure your area has 4G coverage. Its not widespread yet,
Edited by Sneakycyber, 29 April 2011 - 05:47 PM.