It's fun to think you know more than the thousands of people who's jobs it is to manufacturer and ship software for devices. I mean really, if it was a matter of hiring one guy for a few months, common sense would lead you to believe they'd just do that vs. facing the bad press. Common sense would lead you to think that it's maybe more of an ordeal than armchair software developers like to claim.
Well, I would invite you to talk with someone that actually does this sort of engineering. Getting AOSP up and running some basic apps is fairly easy. Getting a performing, stable OS with good battery life is very hard. It's an operating system. Imagine the scope of testing to certify a release. Android changes *a lot* between releases. Every single change you made in the previous release needs to be ported to the new release and tested. And it's more likely than not that the files have changed and it's not simply applying a patch. If you are unlucky, the kernel changes and you need updated version of your drivers. Sometimes you don't even have the source for those so you need to go contract with chip maker or a 3rd party to rework the drivers.
Now consider that every year you ship 8 new devices. Every year there are 8 more devices you to execute this process. 8 more devices for which in every year subsequent to the sale you have zero return on investment. So in three years, you are managing 24 major software releases of new operating system in a year (estimating, a new major version of Android each year). On top of that, a batch of security patches each quarter, that's 192 minor releases in a year.
Getting an idea of the scope?
P.S., maybe there's a reason CM went belly up on the plan for roll vendors' Android dists for them?