I have been playing with this idea for a long time too and finally decided to complete. I loved what the OpenCom guys did and decided to shrink their module and make it a bit less akward. I am pretty familiar with Quectel as we use it at work. So here’s where I’m at so far:
Just wanted to post this to see what the interest in this would be like. The modem I am using is North America bands with 150/50 Mbps so about as good as you can get in 4G/LTE at the small form factor that would fit in an expansion card. I will be making it all open source but considering ordering some to sell too so let me know what you guys think!