I don't think a "Progress bar" would be a possible feature or even useful, as these scripts are being worked on manually. So, instead of scripters putting effort into updating a progress bar, I believe they should focus on working diligently on their scripts. However, it would be more doable and won't hurt if we could have access to the priority scenes list and know who's working on them or has claimed to do so. This way, we can be aware of which scene will get scripted next and decide whether it's worth waiting for the script or just watch it without it.