Problem
I hate it how you can be having a great roleplay in a region, and then you need to break it off because of IC issues, like monster attacks or whatever. Sometimes you don't want to roleplay in real-time, but take your time and spend a while week describing one event. I am sure many weddings or ceremonies have been abruptly terminated because some characters needed to leave the region...
Solution
As a solution, I would like to see temporary message groups to be created. You could send an invitation to roleplay to all characters in a region, perhaps with a small introduction to the subject of the roleplay. Invited characters could then choose to accept or decline the offer, instantly making clear for the starter of the roleplay if there is any intrest in his initiative.
Far too many times I have tried to commence a roleplay, with hardly anybody replying to it. You can say I should write more interesting RP's then, but it's not fun to have wasted an hour working on your text and seeing it was all for nothing...
Advantages
More flexible roleplaying = more fun
Disadvantages
Might make roleplays further restricted (OOC friends for instance)
Might be abused to send regular messages, though I hardly see a problem there