About the only thing I can think of that wouldn't be reinventing the wheel entirely would be to render your video in sections, and embed those sections in order as videos inside of a PowerPoint.
Outside of that, I started think of other things like using Quicktime to setup cue and loop points such that you can go forwards and backwards if you need to. Or perhaps using Flash as the container. A lot of this becomes unnecessarily complex.
Essentially when you're talking about the kinds of dynamic compositing you're doing with AE, the kinds of UI choices and file-format specifications of AE lend itself to doing work in AE and then doing a final render into video. Conversely, PowerPoint is optimized for a general static scene-graph of mostly 2D elements.
Another dynamic presentation type software I can think of is Cinema 4D, but again, that's optimized for a final render.
The subtle strengths of PowerPoint, like forward and reverse, being able to distribute it, are probably only going to be found in it, or programs like it like Keynote.
If your timing is spot on, then just render the AE video and hit play perhaps. I'm not entirely sure what having the entire power of all of the flexible compositing techniques are going to help at the exact moment you're trying to present something. I would think in theory, you'd have that all figured out before the presentation, and then the presentation would be just a replace of that mostly non-editable final rendering.
