I will say this for myself, rather than for the game or for Sage or anything, but I don't give a crap about balance.
If people want to have crazy ability score assignment rules, I'm down, because it'll colour their game. Remember, though, how intrinsic the values become to the fiction you're creating with DW. A +3 in everything is going to mean you'll have some really boring games where everyone gets everything they want. On the other hand, having a -1 in everything is going to need a GM who is capable of a very nuanced approach to soft and hard moves - it puts the momentum much more firmly in their hands.
Tricky, but possible. Let's say that about imbalanced ability score assignment. Sometimes, too, it's fun to just let the dice roll and see what class you'll be based on that. Roll 3d6, write them in order. Pick your class based on what you get, not what you were planning on playing.