Consider using a synthetic deck/fascia board like Trex. They have a moderate amount of flexibility and can be bent even more by carefully applying heat. You won't encounter a rotting problem on any of the pieces you replace with this material.

Google decks. Trex has issues. Check consumer reports. Real wood requires maintenance and will rot, and termites will invade. Yep!

The dude across the street, and down the hill from us showed us his Trex deck. It looked awful! Like a bad sunburn! Peeling and not attractive at all. Their warranty did not cover, so he is stuck.

Beware!

Nothing is perfect, but I still think using Trex for a fascia board is better than using regular wood in a situation like the OP describes. I don't have a deck made of Trex, but I've used it for raised beds in the Pacific NW for four years with no deterioration, inside or out. In comparison, my cedar raised beds start to deteriorate within a year.