I think they attempted something like that (though definitely not on the scale you describe) with Spartan Ops. That was slightly undercutting the 'major release' (with same engine) concept, but attempted to address the recurring storyline release using the existing engine... while trying to balance fun gameplay (ymmv) for the gamers.
I'm on the fence about it.
I'd love to see more from Spartan Ops; but I don't really care in what form it comes... just get more story out there. I wouldn't consider new releases with the same engine in short time scales a "major release" though. IMO it would be more like ODST; some might consider that a major release, but it really was more like a significant interim release with a slightly tweaked Halo 3 engine. That's the kind of short/interim release I'd love to see more of, while the major releases are being developed.

Have a team work on campaign content with existing engines, a few developers to make minor tweaks to work with the release if necessary. Have another team do the heavy engine updates for use in new major releases.
In so many words. Obviously more complicated than that. But that's what I'd like to see more of, personally.