Although I have no experience with these sort of systems, and barely with any aquariums at all, I like you're plan and design, so i figured I'd give you my input on the setup.
I'm assuming you're planning on having an enclosed base for the tank to be setup on, so I would go with a long narrom overflow/filtration tank underneath, close to the length of the tank itself, but narrower just so you don't end up with a huge amount of water there for no reason.
I would use seperate placements for the intake and overflow, for better filtration and flow(rather than just about having your water cycling through the overflow and skipping most of your tank)
I would have an overflow towards one end in the center, and the pump pumping in at the other end.
Structurally, i would definitely go with a very thick bottom, especially with the plan I would use with two holes drilled right in the bottom, and I would use strong pvc tubing at both ends and make sure to have a perfect, maybe even overkill seal on those(since they will be uinder the substrate it seems like it can't hurt to have more silicone than you would need.
I would suggest having the overflow wherever you want the top of the water, and the pump just a bit below that, taking into account how much the volume of water is above the pumps output near the top of the water, and having more than enough room for that in the overflow tank in case of pump failure and drainage, or possibly having the pump plumbing go above the water level, either is merely preference as far as I can tell.
Again, i have absolutely no tank designing, or structural knowledge, so take whatever I say with a grain of salt, but it seems that the modifications I suggest would work as far as the tank cycling the water properly and the overflow working as a filter for the water, as well as maintain your main plan of having the tank viewable and attractive from all angles.
The placement of the plumbing in the tank seems like it would be the biggest decision for you to make, on finding the right balance of having it attractive and not near the edges, and still maintaining enough distance for the tanks water to fully cycle throughout the flow process.
I'm really not that great with descriptions, so I roughed up a cruddy drawing.
Hopefully it helps out, and hopefully you have good luck with the setup, a nice giant tank sounds like a great centerpiece for any room.