This is an old idea that I want to get started again, it's also sort of on the occasion of Assassins Creed: Revelation on the way. The idea spured from the Cristina Side missions in Brotherhood. I made it so the final mission where she dies doesn't happen and it ends where she tells in Venice to never find her again.
Now that Ezio's task has finished and he finally hid the Apple of Eden, he decides to go back to Monterigoni and rebuild. Once done he finds himself bored and the house to be empty a bit, with Claudia now an Assassin and taking on missions of her own and only his mother left at the Villa Auditore . So he sets off looking for adventure once again. He arrives back in Firenze not being back for quite some time, about 8 to 10 years if I'm not mistaken, and enjoys the feeling of being home again, but fears running into Cristina again. He hopes she is still not angry at him for what he did back in Venice, but he knows she still is. So after unpacking his things back at his old home there, he goes to the market looking for supplies, and low and behold he finds Cristina there without her husband which was a shock to him. He keeps his distance until some bandits come, seeing that Christina was upperclass they decide to try and rob her and Ezio acts quickly even only with his hidden blade and dagger. Still showing his skill as a warrior he is able to fend them off and save her and sticks around to see her reaction...
Now this could go a couple of ways, she could either still be mad and he has to try and win her back, another is that her husband has become unfaithful and she finds comfort with Ezio, or her husband is dead and she has mixed feelings for Ezio and stays to try and sort them out.
So if this idea suits you please contact me via PM or just post your interest here if you want.