Well since no one else has posted can offer that you don't want to use anything with silicon in it and if the car is going to be exposed get a shield or cover the dash pad when outside.
I've used mink oil on them in the past without any negative side affects from what I recall. Not sure what the outer/top layer is made from. If we did that might make it easier to figure out other possible treatments. Of course anything you put on is likely going to off gas a bit especially in the heat so be prepared to address that as you find it most likely on the inside of the windshield
Just some random considerations and one suggestion