I asked this in the Cullen thread and Cerulione rightfully suggested that we move the discussion to this group.
In case someone reads this who hasn't finished the game yet, be aware of spoilers!
I'd like to write a story about how the Warden finds a cure for the taint. The only problem I have with this is that my mind is totally empty and I can't come up with a damn cure. So, does anyone has any ideas how it could be cured? Oh, and my fanfic takes places shortly after DAI.
At this point we only know that Fiona is the only Warden who was ever cured of it and no one knows how that happened. I haven't read the Calling but based on what some other users wrote on the forum, she was wearing an amulett that the Architect gave her. But it wasn't just her amulett that cured her. There was also some weird magic going on, so a whole series of events that no one was able to recreate later on cured her.
Then we know what Bianca said about the Red Lyrium. That it's somehow infected with the blight. One of my theories is that it was originally blue lyrium, then got infected and turned red. It might also be connected to one of Thaigs (thanks to Cerulione for pointing this out).