Thank you!
That was exactly what I ended up doing. The steps I took are below.
- Uniinstalled all Sierra Wireless drivers.
 - Installed GenericDriverSetup_Build4581.exe
 - Made sure modem was disconnected.
 - In the DriverPackages dir I ran “DriverInst.exe USBCOMP=8” from an Administrator command prompt.
 - #4 seemed to be critical to prevent the Sierra Wireless drivers from setting the USBCOMP back to 9 (MBIM only). The swi_setusbcomp.pl script floating around the web has been very valuable to check and set the desired USBCOMP mode on an Ubuntu machine.
 - The default EM7305 Windows Generic Broadband driver is installed.
 - Update the driver of the network adapter.
 - Choose Driver => Have Disk => c:\Program Files(x86)\Sierra Wireless\driver package\driver\swg3kmdm00.inf
 - “Sierra Wireless Incorporated” => “Sierra Wireless Mobile Broadband Network Adapter”
 
These are the exact steps that worked for us to get all ports accessible.