I've actually been thinking about the idea myself. I'm currently going through S.T.A.L.K.E.R. Clear Skies (the prologue of Shadow of Chernobyl) to get some information on the world as well as the game. As for the unvoiced dialogue, so far most of the npcs I've seen that haven't been voiced have some sort of headwear or mask covering their mouth, so I have the idea of recording the dialogue myself an editing by either muffling the voice a bit, or using a voice manipulator of some sort, and possibly having someone else I know voice act it. I've got all 3 games, so I think it would be an interesting series to do, to say the least. I'm going to do some more research into the games as well as play through them and start coming up with some ideas for the script and such very soon. If anyone believes that this is a good idea, or have other ideas, or any tips and advice it would be much appreciated.
EDIT: Hmm... although I myself do not have a russian accent and I don't believe my attempt at an accent is all very good, so that could be a problem, though I have a sort of idea of a backstory to try and explain it. Though I suppose it is just up to the viewer.