Heyo! Pretty tired but all is well. What about with you?

It sounds like a pretty interesting hypothesis.
My guess is that it depends a lot on the computer running it.
If you handle 60 fps steadily then it could probably be percieved as the effect you intend.
Around 30 fps or less I doubt it would still hold as good as it could, so you might get a replay that only some people are able to see properly.

Anyhow, it's a pretty top top tier idea for a replay so my advice would be to ask someone to make a script (maybe based on a merging script NutHug has, he never posted it so you'd have to ask him and good luck with that) that would merge two replays in alternating frames.
You'd need to use this script (http://forum.toribash.com/showthread.php?t=439010) too, or integrate its code on the new one, so that you'd have every frame of both replays to be able to fuse them properly.

The only big limitation to your idea honestly is a technical one, since it would require an immense amount of time to do this manually.

Fingers crossed for you to get some help from the .lua or 3rd party programs part of the community since they are less than a handful of people though...
Hacking is indeed desperately in need for a few more scripts.