Replay files only have details of set turns & specific events, everything that happens in between is handled by the game engine.

Without a full 1 to 1 version of the game you'd get a slide show (providing you made a way of converting the .rpl to images), and that slide show would only be for the specific frames saved in replays.

So for example a multiplayer replay would be a slide show of every turn + every time something gets dismembered/fractured.
To put that in context, a full TK match without dismemberments would be a 12 image slide show.

It would have to be a 100% perfect version of the game to do it properly, otherwise the replays wouldn't play correctly - much like old replays don't play correctly in newer clients due to the engine changes (and of course new ones often don't work correctly on older clients).

Or you would have to go full matrix style and look at the replay as a .txt file and say: This tori has a sexy red dress C:

SkulFuk: on a scale from pokemon X to Dark Souls, how difficult would making a phone port be?

Dark Souls with voice commands.

the only way i can see this working is if the replay is RECORDED and saved as an mp4 or something. you wouldnt be able to move it while watching so keyframes and whatnot would be a necessity. This way of doing it is far more reasonable for both the phone, devs, and computer recording it. If this is REALY wanted this is the only way i can see it working.

Don't think it's necessary to create option like that. I prefer creators spending their time with KO option ;)