Considering how confusing some of the characters' existences have become (Roxas with Sora's body and either resonating with Sora's heart or housing Ventus' while Sora keeps going as a pseudo-heartless, Xion's transient existence, the whole Terra-Xehanort/Ansem/Xemnas/Lingering Will mess, etc.), I was contemplating how all of these would get "resolved", and came up with an idea. Instead of giving Roxas his own separate existence, it would be cool if Roxas was actually a part of Ventus' heart and not Sora's (apart from the two still being linked), meaning that Ventus would inherit all of Roxas' memories and experiences (including his friendship with Axel/Lea) when his heart is finally fully restored, in addition to all of his previous memories. This would effectively restore both characters at the same time, and it seems entirely plausible (at least to me) that Ventus' heart could have formed Roxas' personality as a sort of intermediary step toward regaining total consciousness.
On a related note, there is an issue bugging me about Ventus' revival. Once Ventus separates from Sora, I'm a bit anxious to see if he will lose his ability to dual-wield keyblades. It might seem a bit petty, but let's be honest - it is by far one of the most awesome features in the series, and quite a distinctive power unique to the main protagonist. He didn't dual-wield at all during the Mark of Mastery exam, however, so I don't know what's up with that. Best case scenario, the two of them stay linked to some degree and are BOTH able to use each other's keyblades.
Please feel free to comment on anything you'd like to add, subtract, or modify about either topic. I'm also interested to see all of your ideas regarding how the other characters will be resolved.