Alright guys, after some thought this is what I have come up with:

The roleplay will start in Columbia and end in Rapture. There are experiments taking place in Rapture that are similar to the Lutece experiments on Elizabeth. One of the test subjects has managed to escape and has found their way to Columbia, in search of Rosalind Lutece to find some answers and help for the others still trapped in experimentation. Shocked, Lutece seeks out the help of a secret society based in Columbia (name to be determined. This is where a lot of our characters will come in.) The society agrees to help, and heads to Rapture to free the victims and end the cruel experiments. At this point, Rapture is between its prime and its ruin, so there are a fair amount of splicers and chaos but it is still a habitable city. The experiments could be taking place on the rescued Little Sisters or just innocent citizens, maybe by Dr. Lamb. Dr. Tanenbaum could also come into play, along with Andrew Ryan, Sander Cohen, and Fontaine. 

So guys, go ahead and tell me what you think. Feel free to suggest changes or additions, :) I hope we can get this off the ground soon guys!