Given that many larger businesses are already going to have well established workflows around PowerPoint presentations that are going to be hard to shift, you may be better trying to control the ‘analytics’ portion of the value chain rather than the presentation creation segment.

Have you considered building a tool where people could upload their existing PPTX presentations into Sizle and access analytics on them? I can see that adding real value. At the moment you are probably limiting yourself to SMBs and freelancers.