I have a simple suggestion.
What about creating a new paid feature - for some amount of money (I think symbolic 1,99 € would be nice ) there will be a possiblity to buy a version of game (which you already own in your library) for another platform.
And it would be nice if there will be opportunity to share saves between 2 platforms, but thatīs just a detail.
I think itīs a good suggestion, cause it provides money for Ubisoft and cool feature for users. If this will be implemented I will convert 3 games (that means +-6 € for Ubisoft).