Greetings,
This is a weird idea (I know I'm probably gonna get flamed for this), but it's something I've always thought would be immersive and cool. Its a "alt" development system which simulates having a child and raising it.
Basically, at max level you would be able to marry a friend, guild mate, or even a NPC if you are a solo type player. Once married, after doing a quest chain together, you and your mate would have a child (or 2 depending on if your partner wants an alt to raise as well). Once completed, your child (aka alt) is born. You name him/her and basically bring him around with you kind of like a pet companion. He/she gains experience from everything you do (maybe up to level 10 or something small). This will indicate that he/she is full grown and is able to decide on a class/professions. Once class/professions are selected by your raging teenage child lol, you will be able to play that character as you would your main character, and maybe even gain an additional ability relating to his mother or fathers classes, just as a perk. You can continue to do this and theoretically create a "legacy" or "bloodline" for your characters. Maybe even an option for your child/alt to choose the opposite faction as the parent characters with another cool side quest chain that involves some conflict within the family.
With love,
Joda
I like the Ide its like a Pet but in common with someone ingame so not just 1 person is attached to it but 2 people are