I upgraded from an Acurite 5-in-1 to the Weather Flow Smart Weather Station (and now a Tempest). My old Acurite station was set up to take a 3/4" pole and the Tempest uses a 1" pole. Rather than take my pole down and replace it, I created an adapter sleeve and 3d printed it. I uploaded the file to Thingiverse in case it could be useful to someone else in the future: https://www.thingiverse.com/thing:4618786
I was looking for a similar solution as I put up a J-mount antenna setup and put my Acurite on it. What worked for me was a 24" 1" ID SCH40 PVC and it fits snugly on the existing pipe, which in turn makes for a snug fit of the Tempest. I had purchased another part that the Tempest would have fit on, but I wanted more height. The j-pipe was filled with small rock and the PVC was filled with sand to counter vibration issues with winter coming.
I like your idea, though.