I like multi-classing's concept, but sometimes it isn't done right. In a game like this I wouldn't want it to turn into Skyrim and be a sneaky mage in heavy armor, that's great in Skyrim but not everything needs to be the same. I guess you could say I want specializations, stuff that kinda branches off from the main class because of another class' influence but still being rooted in that specific class; and for it to happen not too early, you need to establish your character before you do advanced development. Say you have a rogue, you level him up to level 12. You then can choose like one of two broad branches, delve into more brutal physical attacks or add some magical effects to your arsenal. After that you could expand the branches even further creating a very distinct specialized character.