It would be nice if we could trade heroes between players.
This feature has been discussed a lot in the Android forums.
I don't think it will ever happen simply because it would be abused greatly.
For example, lets say you have learned that your account is suspended. After you get your account back, what's the first thing you would do? Trade all of your high level heroes to another account.
There's just too many ways to abuse a system such as this, that it would be bad if it was implemented.