I think some of the problems with sidequests can be solved if
1) they're not usable for grinding
2) they're not purely modular
The first problem was already solved in TW2: kill enough of one kind of monster and you gain exp fighting that particular monster. Keep killing more of that kind of monster and you get very little exp. In other words, experience is enemy-specific and also general. General exp allows you to level, while enemy-specific exp allows you to get better at fighting that particular enemy. If the amount of exp gained from side-quests was also either specialized in some way or limited, then it wouldn't be possible to generate an overpowered (and therefore boring) Geralt just from side-quests.
The second point is more difficult to implement, but it is the foundation of every good RPG. The quests should influence the choices and outcomes of other quests. It shouldn't be possible to "pull" a quest out of the game without a domino effect on everything else (i.e., the quests shouldn't be confined to their own modules -- they shouldn't be modular). If done right, the side-quests shouldn't be unlockable until the main quest progresses.
Some of the other ideas in this thread have also been really good. Geralt should talk to himself and remind himself of the urgency of his main quest, and also the NPCs should do the same.
1) they're not usable for grinding
2) they're not purely modular
The first problem was already solved in TW2: kill enough of one kind of monster and you gain exp fighting that particular monster. Keep killing more of that kind of monster and you get very little exp. In other words, experience is enemy-specific and also general. General exp allows you to level, while enemy-specific exp allows you to get better at fighting that particular enemy. If the amount of exp gained from side-quests was also either specialized in some way or limited, then it wouldn't be possible to generate an overpowered (and therefore boring) Geralt just from side-quests.
The second point is more difficult to implement, but it is the foundation of every good RPG. The quests should influence the choices and outcomes of other quests. It shouldn't be possible to "pull" a quest out of the game without a domino effect on everything else (i.e., the quests shouldn't be confined to their own modules -- they shouldn't be modular). If done right, the side-quests shouldn't be unlockable until the main quest progresses.
Some of the other ideas in this thread have also been really good. Geralt should talk to himself and remind himself of the urgency of his main quest, and also the NPCs should do the same.