The Innovative Marine 50 Lagoon with a custom stand sounds like a great idea. Its dimensions are 30" L x 24" W x 16" H. As suggested above, an all-in-one (filter in back of tank vs sump) and a shallow tank would be best. You can also get that tank in an external overflow version if you did want to have a sump plumbed to the side of the tank on its own custom stand. In some ways that would be easier to maintain, but unsightly in your living room depending on your taste
. Vertical space in a reef tank can make it look cool and add drama, but ultimately doesn't provide much use unless you want to grow really tall corals. I love the dimensions of the IM 50g tank because it maximizes the surface area by keeping the height short. I think this would make for a maintainable tank for you, especially since the 30"x24" footprint can easily be accessed by all sides (assuming you can put it in a place that would allow access like that).
I'd definitely suggest some LED light source like the Kessil A360x or equivalent. That way you don't have to stress about changing bulbs like you would with a halide or T5 fixture. It would also be less bulky and stay out of your way when trying to get in the tank. You can get adjustable goose neck mounts for your lights so you can hang them off the back of the tank and not have anything obstructing your access from the sides.
Depending on your budget, something like a Neptune Apex would be nice because you could manually control the outlets, so if you need to unplug something for maintenance you don't have to get to your power strip (this could also save you from having to mount a power strip in an unsightly place).
Water changes will be tough if you don't want to do some plumbing. You could get hardcore and plumb your tank up to a mixing station so water changes are a matter of turning valves, but that's pretty involved. I bet you could configure a dolly of sorts that would bring the buckets to an acceptable height so mixing, siphoning, and draining isn't burdensome, and moving the buckets around the house would be easier (unless you have stairs).
Everything else I do with my reef (testing, mixing stuff, trying not to spend all my money on gear online, trying not to spend all my money on livestock online, trying not to spend all my money on another tank online, etc) is done sitting so I imagine those other tasks should be doable.
Don't forget to start a build thread!
