No, you misunderstand completely - the statement of "mission drives the train" doesn't have anything to do with institutional inertia or closed-mindedness.
It simply means that the purpose of the project should dictate how it is attacked.
As a concrete example, someone looking to by a small, economical commuter vehicle most likely wouldn't cross-shop a large luxury SUV - and again the same for someone looking to blow a few hundred grand on a track-toy.
Mission drives the train simply means that we should look at the final goal, first, and work up ways to get to that goal.
Translated to what
justahop is looking for, this means that he should first clarify what he wants out of the gun - and then look to fulfill those requirements.
And towards this end:
You're good-to-go in today's market with that kind of budget.
I'd go all-out, given the home-defense part of your equation. Don't do sub-par parts.
I'd shop at G&R Tactical, Big Tex Outdoors, Rainier Arms, SKD Tactical, Primary Arms, Operational Detachment Source (ODS), and Weapon Outfitters - all of these retailers stock components from vendors which are considered to be duty/defensive-grade .
Sionics Weapons Systems, Sons of Liberty Gun Works (SOLGW), and Bravo Company (BCM) all maintain their own websites, so their parts can also be procured directly.
And sometimes, when the smallest parts aren't available via the smaller vendors, I'd go to Midway USA and Brownells. Both offer excellent search engines that can help you pin down even the smallest component. This was actually how I built my small stash of spare components such as extractors, springs, etc.
You honestly should be able to put together a premium defensive weapon for that price, using nothing but the best, if you don't go crazy on Gucci stuff or really specialized items (i.e. a Hodge Wedge Lock rail so that you can mount your MAWL
).
It took me 4 days to work though - but it's listenable as there are no visuals, so if you have a long commute, that would be the way to go (it'll be like sitting in on a conference call).