Hey. First off, nice post. By far the clearest I've found on the subject. Not having much joy getting 3g going on my pi though. I get 'failed to connect' everytime. I'll list my process-
Using Huawei E3231 on 3 (UK)
Latest wheezy raspbian (fresh install and updated)
Dongle works as expected under windows
lsusb = ID12d1:1f01 (is that the issue?)
Followed your instructions
Get same error everytime

I'm still pretty new to all this so I'm finding it hard to even search for a solution. I'm trying to get my head around usb_modeswitch.
Unfortunately, I've not come across any reports of this device working with R-Pi. There must be a solution though(fingers crossed). Any ideas? Cheers