The problem is that it will then become an interactive powerpoint, not a whiteboard anymore. It sounds more like a new product to me, not just a simple new feature.
Actually, it is a very commonly used feature...many teachers using online whiteboards for tutoring will upload a preprepared word doc/ppt worksheet and then the student will write in the answers.
If teachersare going to use this, many of them will already have a powerpoint to use.
Adding to this, an easy way to navegate betweens different whiteboards of the same author (so it is easy to go to the next slide).
Just my opinion about what might work.