I already said I will do writing of at least one section of the story as well as writing the parts to weave stories together. I have pieces already planned out for a section, with a rough sketch of the map it will take place in and the plot piece of the story. (If you want to be in this section send me a PM)
I'll also work on monster sprites but I need to know the orientation of the battle before I start on them. Would be useless to have a monster side sprite in the front/back oriented battle.
People who can not use PRG maker itself can contribute with concept art.
As for random battles why not remove them for the most part alltogether? Have random monster sprites walking around dungeon rooms that if the player touvhes them the battle starts. Some dungeon rooms can have random battles, with a title like "room of hidden foes" to give them an added effect.
If different people work on different sections then it is really important that you let other scenario writers know who you are using. If Rye is the queen who gets killed in one section of the game, the barmaid in another, while in a third the main character then it gets really convuluted and falls apart. Especially if the barmaid hires the main character to kill the queen.