This may be the reason the Alliance never bothered with them. Since they'll burn themselves out anyway, why bother wasting resources or getting more people involved who may say something to the civilian populace since they went out of their way to deny their existence. Then, once they're all gone, start the project over again, just like Mal mentioned in the movie. I don't have too much problem justifying the differences in them from the movie and the series. I always took what the rescue team member said about them as more of a description of them than an actual medical explanation. Sort of like saying "That person is crazy". While it's a specific description, it doesn't mean it's completely accurate. Just like the descriptions going around of the pilot in Texas.
That's kinda the problem, though. The TV reavers were insane (but could be probably extrapolated to be fine as a group). The MOVIE reavers had their aggression response pushed past the maximum (the opposite of the people that died, that got so passive that they just laid down and died) and weren't insane, or stupid, but in beserker rage. Can't maintain a system like that for very long, and I'd imagine it would burn itself out pretty quickly by either killing the host or having the hosts kill each other.
the TV system was workable (although granted there weren't many details on them, but from episodes like where the kidnap victim emulated them, you can guess at it), the movie system doesn't hold up.