I was thinking of a change in the quest system. Basically, initially the number of active quests you can have at a time is 5. But that would increase to 6 at level 40. It would increase to 7 at level 60 and 8 at level 80 and so on. It makes it more difficult to be bogged down in special quests, particularly later in the game and reduces the need to abandon quests.
One issue with that is sometimes you do run out of main quests like at higher lvls plus the special quests can be fun and can be worth taking too.