I wondered about this. In my experience, every SIP provider seems to have their own API for sending and receiving SMS through their SMS enabled trunks. The only thought I had was some type of provider template similar to how we handle SIP trunks now in 3CX. But that seems like an ugly mess given the fact that there really isn't an API standard we can rely upon.
How does using a global SMS carrier work if you want to send and receive SMS from your business's primary phone number? Does that mean you have to port your phone number to this cloud SMS provider? Either that's an unacceptable approach, or someone knows something I don't (which is very likely).
Dang, if I knew it was going to be another year, I probably would have bit-the-bullet a long time ago and built a solution myself. Now I have to ask myself, is it worth risking investing the effort (money) to build a solution only to have 3CX provide the capability in a year or so, or do I just wait and hope it doesn't get delayed 2 or 3 more years. What to do...