If you Don’t care about controlling the Fan, then do exactly that. If you already have Caséta and you want to throw in some fan control there then change the switch for a Caséta fan control and then just get a two gang plate and mount the pico flat on the wall with their adapter right next to it. It will look like you have a two gang box even though it’s just one. This is what I have done for our fan downstairs.
I have two other fans with the aforementioned Inovelli LZW36 light and fan controllers. While I like this controller, it’s ability to disconnect from its module and control smart bulbs is lacking at the moment. There is no hold and release for dimming, so that is clunky and it’s slow to respond as a button Controller. If they can speed it up and add hold and release to the dim buttons, then it has very nice features such as the indicators and being able to set them to almost any color and pulse to identify different states around your house like doors unlocked, etc.
However since the Inovelli require a separate module installed in the fan canopy, the Caséta is a much easier fan controller to install. But you said you don’t care about fan controllers so your idea is perfect and exactly what I’ve done in many locations around my home. Picos are the best solution for a home in my opinion. They’re durable, capable, reliable, long lasting and they look nice