As far as depth of a tank goes, anything beyond 30" deep will be a problem. A five feet deep tank would be very impractical - not to mention extremely expensive. Both for lighting issues and you won't be able to reach the bottom - unless you have diving gear handy.
I can understand you wanting something unique, but unless you have a good bit of DIY experience, this could be an expensive endeavor for you, because it costs to redo stuff that doesn't work right.
I would go with Patrick's suggestion and get a 200 gallon reef ready tank and have a mixed reef. Put the tank at a comfortable viewing level in wall and make it like a big picture window to the ocean. That's what I would do - if I had the room. I actually had a 200 once and it was my favorite size tank. A 200 gallon in wall tank full of corals and colorful fish is a definite WOW factor!
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