Welcome to the forum.
As a DIY kind of guy, I snoop out (steal) ideas constantly. Reading your post, I realize I have yet to see a "Housing" in any detail that I liked.
I cant help with plans.
A few items though:
1. Cable chase underneath that runs to your rack. (NOT just wire under the carpet)
2. A vent grill near an external or the projectors built in fan. ( vent the heat to a side or the front: not in your face, eh?)
3. A removable top or side panel for patching/ cleaning/ etc.
4. A slot inside for the manual to live in could be handy
5. A recess for the remote.
6. Glass top for style.
As my floors vibrate and rumble I think I would want to "decouple" the projector shelf inside while the housing was wieghted and spiked to the floor. But I dont know.
There is a nice looking unit in Audio Video Interiors, Sept. pg. 50. You might take a peek at this but theres no details.
You have a solid floor under foot? jdb