Several Suggestions

L
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1. Finger print lock, instead of a normal lock. Finger print locks are unpickable, which is something L should have, to prevent people from just random picking, and then stealing his items. It's pretty much a door only L can open. An option to assign other players the ability to use the doors would also be nice. This would add to the realism of the station, it being something that no one should be able to break into.

2. Cameras / Bugs would be a great addition to L's gadgets. He could place them in certain places so he could spy, etc. Cameras and bugs in the L building would also be nice, so s/he can see what's going on without ever having to leave the privacy of his room.

Kira
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1. Remove full page / remove part of a page should be brought back. I don't see why it was removed in the first place. But yeah, and option for taking out a full page, or just a piece of a page would be useful.

General Public
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1. Actual lock picks would reduce the amount of people who just randomly go around and pick stuff. You would NEED a lock pick, to pick locks. Once you have your high intelligence, and your lock pick, you would go, and attempt to pick a lock. That's where you're given a minigame! This would be more realistic, because it would lengthen the amount of time it takes to pick a lock, which is a great deal of time. The minigame should be some what of a challenge, of course.

Losing the minigame would result in your lock pick being destroyed, because you messed up. You can sell them at the same dude who sells fake IDs. Raising the prices would result in less lock picks going around.

M should start with about two of these, but would have to buy the rest.

2. Apartment complex / giant hotel like in the original DNO. People could go in, purchase rooms, etc. It'd give players temporary homes, which they could use to store, and secure their belongings.