Uh, maybe you could do something with strawberry cake or apples. With the idea of "L's corner" that arneth-san came up with. You would have three different point's of view for the same puzzle/quiz. One in Kira's point of view, one in L's and the last in the criminals (because they don't think the same). Then when you finish the puzzle/quiz you get a piece of cake for L's puzzle, an apple for Kira's and a weapon(or something) for the criminals. After gaining five to ten cakes/apples/weapons you get one wisdom point. After gaining ten or so wisdom points you get a VERY little bit of information on an opposite group. In the end it would be very hard to get information because to gain that little bit you would have to get 50 or 100 cakes/apples/weapons meaning you would have to solve 50 to 100 puzzles. But you could also make it where earning cakes/apples/weapons doesn't and can't come only from solving puzzles/quizes. It can be made were you have to have at least 2 or 3 wisdom points from two or three different puzzles/quizes. Which mean's the creator-sama would have to make two or three (or more) puzzles/quizes AND have three different point of views for each one.
Or
Instead of getting only information you could also gain an alias after 50 or 100 wisdom points. Which would also split up jobs in the groups. While some are smarter they would gain an alias and someone else would gather information because it takes a less amount of work. And you would want someone smart being the alias anyway. Of course that would only be if you were splitting jobs in your groups, who ever wanted to have one could. And because of how many wisdom points you need it would be 500 or 1000 (or more) cakes/apples/weapons. So you would have to be carefull.
It would be a lot of work to do so though. Very hard to do.
And
About the Shinigami problems. Maybe you could make a "sister" site. As in people could sign up to be Shinigami there. The sites could be conected by a chat. But, ONLY people who have Death Notes or an alias could talk to them and ONLY Shinigami with HIGH points could talk to those Death Note or alias owners.
Or
Instead of an alias they can have a Shinigami from the "sister" site. Their Shinigami would be able to get information the same way. By the puzzles/quizes with three different point of views.
And
To make it where you can only take one point of view puzzle/quiz and not gain other information(such as what the other groups know about you), you have to register to a group. And thus can only take that groups point of view puzzle/quiz.
And
The information the Shinigami gets would be different from what the Humans get. Such as they can get information about other registered Shinigami working for other groups. Thus getting their information.
And
When you get enough points for an alias you can pick to get that(an alias) or a Shinigami. Of course with an alias you would get different information than you would from a Shinigami. And Thus splitting the work in your own group.
But
This is all just my random thoughts. Gomen-nasai! I'm thinking too much! Gomen-nasai!
*Hm, This is the most she has ever written...of her own free will...* Hey! Ryota-kun! Don't be so mean! *Hai, Sorry, idiot* Gah! You baka!
*Same thing...

*
Hmph! Fine! Anyway Domo arigato!
Yatikami, Mei-chan
And
Ryota-kun
