[andy]

A possibly slightly bulkier idea, but how about a router which you plug a dongle into, then the dongle could be replaced when it was deemed necessary?

I have a Draytek VoIP router which I picked up very cheap, and there's a software update to enable using a dongle in the USB slot, though I haven't actually used it yet.

Another potential point is which Mifi devices have a socket to allow using a better aerial if that would be helpful