Sounds way too complicated. Why not use an eSIM (if you have a newer phone) for the data line when you are out of the US. You could keep Xfinity as your main voice line and use another provider like Google Fi, Airalo or Ubigi for international data. I do that when I travel internationaly and it works great. Otherwise it sounds like you can only suspend your Xfinity Mobile service for up to 14 days at a time.
I do plan to do something similar to what you are doing, but the only difference is that I would use Google Fi for both data and voice/text and not want to use Xfinity Mobile at all (it's cheaper to use Fi for everything).
Also, I contacted another representative, and got a different answer. This time, I was told that there system does allow me to cancel and re-sign up as much as I want to. I guess I'll have to try this to find out for sure.