i think making a sequel of the game at this point might be hard, aside from legal, technical, and monitary challanges, the bigger problem is calling back the voice actors. Then again, these days there are a lot of talented people who can imitate other voices.
but nothing should stop if you're going to write a good story, or if you just really want to write one. as for help, i'll do my best. throw me stuff when you can and i'll try to give constructive feedback.