Aye, as I mentioned in another thread I think we ought to settle the question of the script before tackling that of the voices.
While it would be possible, of course, to let people imitated characters' lines from the movies, I don't think this would be the better approach over having the script first. If we do the recording and voice picking before we have a proper script ready, I'm afraid there might easily be a decrease of interest in the project in case it takes a longer time for the scripts to be finished after the choosing of the voices. If we can continue the recording right after the selecting of the voices I think there is less of a risk that the "impetus of enthusiasm" for the project may be lost due to long waiting times.