Or even just redo it. I can't imagine it would be that onerous a task to crowdsource it out to like-minded enthusiasts - and some of the VA in FO3 was hilariously bad (I'm thinking of do-over lines, mispronunciations, monotonous delivery of some dialogue), so what's the worst that can happen? I'd happily sit there and crank out a few thousand lines of dialogue.

Release it with silence for the voice acting, and include the script and a utility that lets you and your friends record yourselves doing the voice acting and inserts that into your installation.

Make a way for people to distribute their versions of the voice acting for others to use.

Good question. But realistically, a mod like that would also need an installer software able to pull and convert also: textures, meshes, game plugin data, scripts (and perhaps some other misc stuff I overlooked), or creatively recreate some of these from scratch, or have permission from Bethesda (against the company policy, I am afraid).