This is just a feature request for the far-off - but over the years Sufferfest has been, in my opinion, the best indoor training partner available. It pushes me to efforts I don’t usually make, and recently I have been using the PeriPedals integration with my Kickr to try out a resistance matched workout.
However, if there was a Zwift/Sufferlandria alliance I think it could be incredibly immersive - especially when it came to group workouts - the one thing that Sufferfest can’t do is let you race head to head with friends whilst doing the workout. So there would need to be a group mode for Zwift, with a synchronised start - and then potentially a video-in-game stream (maybe a pay per use model for the videos). I can see this being huge for Zwifting studios - especially with the licensed music, and you would end up with a Sufferfest score based on wattage or distance.
It would not be possible to design a conventional landscape for this - as hills would have to last for 5 minutes for everyone, rather than 2km, but a visual representation with countdowns to next climb etc would be possible, and the visuals would be built around the sufferfest video.
The next challenge would then be Ghost racing against yourself, friends or KOMs - and I would guess the ultimate metric would be distance - so you could have a 50km Angels target, or however it worked.