Re: scratches and alga - That Kent pro scraper is not adequate in my opinion, and those Kent scrapers don't do an adequate job with calcium-based alga at all in my experience. At that depth its (debatably) impossible to keep those viewing panels free of scratches and coraline. As you know it just takes one tiny grain of sand or one tiny fleck of coraline to get between the scraper and the panel, and it's all over. Wish it wasn't so, believe me. No matter how careful you are though, it's inevitable.
I really hope you are right for your sake, but I'd bet in a year or two you'll have a lot of scratches and a LOT of coraline alga all over that tank ruining the view. This is not your first tank either I assume, so I'm surprised you're not worried. Usually the #1 lesson people say they learned after a tank or two.... is that glass is the only way to avoid the creeping mess that ruins the scene. But again, not sure this project would even be feasible with glass, anyone know?
Re: wires and visible equipment - I see what you mean from the image of the crowded tank, but based on your existing aqua-scaping I assumed you were not going for the old 2dimensional overcrowded 'fruit stand' look and that's why I complimented it. But if that is the look you're going for, then yes, in 3-5 years it might be crowded enough to block most of the wires etc. It's unfortunate that all those wires and powerheads have to ruin the clean, uncluttered scene that was first envisioned in your plans/renderings though...
Re: redundancy measures - I not sure that a controller will account for certain things. I'm assuming you have a plan when the chiller dies, or the main pump dies? Sometimes it's not enough to have replacements in stock... if you're out of town or cannot get to the tank quickly for example. What's the backup plan if the chiller or main return pump dies?
Again, thanks so much for sharing!