There should be an option to have locked chest available for buying. The concept is quite simply that the player that lays such a chest can demand that a special password be enterred before the chest is opened and possibly he has the option to provide some descriptive text before it's opened (in order to provie a hint for example).
These chests could then be used for missions or generally for more interesting stuff.
In order to make them more interesting/rare (so that not everyone has them). Perhaps allow them to be bought only by benefactors or level 8 or more.
There is certainly a demand for puzzlemissions but currently players have to rely on workaround in order to get it to work (i.e. tinyurl to block the next step until the hint is found).
These workaround don't always work (personal experience) and don't give as much options as possible.
So I would like to suggest that specialized tools are provided by PMOG to make such puzzle missions. Examples are:
* Roadblocks: Allow the player to place a roadblock between their lightposts that the mission runner must work around. Perhaps the roadblock will open a page in pmog with instructions (written by the mission author) to the player.
* Crossroads: These allow the mission author to split or merge the mission paths at this point. This would allow alternate endings or dead-ends
* Finish Lines: A special type of lightpost that will give a reward to anyone who finds it. This would allow the mission author to provide rewards to runners without having to rely on crates which may be found by random people and cannot be refilled easily.