Actually, your situation is much more common than you think. Hopefully though, whoever built it for you has some experience with constructing to allow for passage of cables between the equipment. If not, you will most likely need to invest in a hole saw kit, at minimum, to provide openings to pass the cables through. Yes, you are correct, you will want to use cables longer than necessary, as opposed to if you had rear access. They should be longer though than just pulling the equipment forward. Ideally, you want to be able to pull the equipment forward, rotate it 90 degrees and slide it back on the shelf. That way the equipment can be supported by the shelf while connections are made. On my own built-in system, I put the shelves on metal ball bearing slides (the type used used in electronic equipment racks) so that they pull out several inches beyond the front. Don't forget you'll need to mount some power strips (surge protected) in there as well and provide access to an outlet for them to plug in to. You'll also need an access opening for bringing other cabling into it such as coax, CAT5e, speaker wiring, etc. If it has doors that block equipment, an IR repeater will also need to be installed for the remotes to work.

To answer questions, yes we gutted and opened up this home. We want our family room just inside the front door as it functions well for watching children playing outside. (Rather than a formal living room, but we want to create a NICE space) The dining room has the fireplace and is open to the kitchen, which has an amazing 10’ island with a bar height side with 4 seats and then a counter height end for food prep. We’re loving the kitchen tho still waiting on light fixtures and backsplash. The flow is working well for us but the furniture placement and how to highlight the fireplace and it’s area is the challenge! Thank you BTW we DO have another room that would serve as the formal dining room but we don’t have that need at this time and are using it as a lovely home/mom office and playroom, so toys stay in there and not all over the house.

I’m not a designer but I think your instincts are right. If everything else is super light I agree the sofa will look too dark and heavy. I think a light, warm neutral paint would be great, and accents of blue would make that gold sofa sing. I think your existing neutral walls look okay, actually. What if you just tried painting the red accent wall a nice mid tone blue?

Coordinate the electrician and carpenter work. When the carpenter tears open the wall and before the window get installed is when you want the electrician to do his work. If the electrician comes before, the wiring he runs could be in the way of the windows; if he comes after, it may be very difficult to run the wires. The electrician will appreciate having an open wall to work with. You also need to try to figure out what is in those walls already: there could be plumbing, electrical, and/or air ducts in there, and any one of those will complicate the job of installing windows. I'm also going to mention that the location of the tv so high up on the wall is terrible ergonomically. While many people locate a tv over the fireplace because it seems logical, you ideally want your tv to be at a height where the middle of the screen is at eye level when you are seated, rather then having to crane your neck up. If you must have the tv on that wall, at least get an articulating, fireplace tv mount so that you can lower the height to a better location when you are watching it. Something like this style: Fireplace tv mount