Hey there!
Got some time and motivation today as well, so I worked on the Shutter Control Handler/Thing. It already works for getting the current level and for the Up/Down commands to move the shutter up/down. I still have to review some parts and add the command for setting a specific percentage value.
I am working on a branch, so you can easily merge it into the main branch once it is in a good state. I already created a draft for a pull request if we want to discuss the code: https://github.com/stefan-kaestle/openhab2-addons/pull/2
During my work I found some things that don’t seem to be correct. Is it okay if I open some issues in GitHub for those, @skaestle? We can discuss them there one-by-one instead of in this thread. You need to enable the issue tracker in your GitHub fork first (https://softwareengineering.stackexchange.com/a/179470).