Looks like you have a good handle on it, and your initial approach seems viable to me. I would think that limiting the number of active quests a toon can have is wise at this point. Once you get started implementing it, I'm sure you'll come across other challenges. As for tasks, I'm mostly familiar with these...
This is an example of a collect task:
http://everquest.allakhazam.com/db/q...tml?quest=4320
This is a combo kill/collect:
http://everquest.allakhazam.com/db/q...tml?quest=3065
I know we're not up to DoN yet, but these tasks are examples.