Film Score/Video Rack Extension
It would be awesome if Propellerhead or even a 3rd party company developed a Rack Extension that let you import and synch video for film scoring. This would be so much easier and faster to do right inside of Reason. It could have the ability to strip audio from imported video and use a hotkey (like F8 or F9) to maximize/restore the rack extension for easier viewing, for starters. Also, having the ability to move the video rack extension to a secondary monitor for editing would be great... You could call the video rack extension "Score".
In my opinion, audio analyzers (which I'm sure iZotope will slowly release as individual rack extensions... at a user friendly price, of course) and film scoring capabilities are the only things missing from Reason at this point. I really think something like this would put Reason up at the top of the DAW food chain when it comes to people doing music for TV and movies.
And hey, lets not forget what kind of awesomeness might come of this for people using Reason for live performances. Reason "Video" in the likes of Serato Video, anyone?