Hey @Spessanon,
Forgified Fabric API sure seems like a useful project. However, the main hurdle for making Wurst work with modern Forge isn't the API – it's about the proprietary Mojang mappings that Forge uses.
Wurst is built on Fabric's open Yarn mappings, and changing that would mean a full rewrite of the client, plus potential issues with the Mojang mappings license.
That said, Forge-Fabric compatibility layers are improving over time and it's something to keep an eye on for the future.