[otr]

I'm sure there are mods (https://mods.factorio.com/) like that, and if not feel free to write one (https://wiki.factorio.com/Modding#Creating_mods).

edit: now that I think about it factorio is purposely deterministic because otherwise it would break multiplayer almost totally.

[billfruit]

May be possible that it can be modded in, but I get a feeling would likely break the game, and things will go out of balance, since the core game perhaps was not designed for such probabilistic behaviour.

Actually some amount of probabilistic behaviour including variation in the quality and rate of outputs of machines, even atleast variability between the different instances of the machines of the same type would have made it vastly more interesting is my view.

[bspammer]

There is probabilistic behaviour in the game for reprocessing uranium [1], presumably they found a way to keep the RNG in lockstep across clients. I'm pretty certain it's possible to make a mod that does what you've described, but I'm also pretty certain it would make the game less fun :P

[1] https://wiki.factorio.com/Kovarex_enrichment_process