Yes, the balcony door sensor is also one of the new energy saving features, along with the glass in the balcony doors are made to resist the hot heat coming through. The blank card must have been in one of the cabins that were open for viewing, or as you say, a cabin steward might have a blank one as a master.
Another new energy feature I've seen recently in Europe is the hall lighting of hotels is motion activated. The hall is dark when you open the hallway door. When the sensor picks up motion, the lights come on. The lights go off when it senses no more motion. No, you can't outsmart it by trying to dodge down the hall.
We booked our New Years' cruise on the Epic almost a year in advance, and I am sad to say that instead of looking forward to the cruise, I am dreading it. No woman of reproductive age wants to contemplate the possibility that she'll have her visit from "Aunt Flo" during her cruise with her extended family, who, should they happen to visit her cabin when she needs to use the facilities, will surely notice that she washes her hands at the tiny sink BEFORE going to the toilet area (because most women who want to avoid Toxic Shock Syndrome do wash their hands before inserting a feminine hygiene device - euphemism used as this is a family type site), then she goes into the toilet area to insert said feminine hygiene device knowing full well that said family can see what she is doing through the glass, then she comes out of the toilet area with an obvious need to wash her hands, in full view of the inlaws, cousins, and nephews. Assuming they do come to visit, since the couches and sitting areas are obviously not conducive to family entertainment. I have been on 3 other Norwegian cruises and LOVED them, especially the Jewel. When we were told that they were launching a bigger, better ship, we thought that meant bigger, better cabins and entertainment. Instead, we will be super-cramped, there will be water damage to our belongings from the ridiculously useless sink and shower areas, and we'll have LESS entertainment since you can only book the big shows once per cruise, and there are only two of them (one of which you have to pay a lot extra for). Sure, they have the Blue Man Group, but I can see the Blue Man Group on land in many different cities. Sure, they have great food, but you'll end up paying lots extra for most of it because they deliberately undersized the 'included' restaurants to force people into the paying venues. My family refuse to cancel the cruise, all because the nephews want the blasted waterslide, so I have resigned myself to hiding out in my cabin the whole time, reading a book. I will boycott Norwegian's stupid bathroom design (did it not OCCUR to them to test this with a real traveling family before building it into a huge ship) and their obvious attempts at extortion (charging for so many things that are free on their other ships) by refusing to order alcohol, refusing to go to the restaurants that require a cover charge, and refusing to buy any shore excursions. I encourage my fellow guests to do the same - it would be awesome to have an entire cruise where everyone refused to go to the restaurants requiring a cover charge. THAT would remind Norwegian that the cruise is about the welfare of the GUESTS first, and the welfare of Norwegian's wallet second. You have to take care of the first to take care of the second. Sadly, they seemed to know this back in the day - they were truly a great cruise line, once, and I hope they can be again.
It sounds like you've already convinced yourself you won't have a good time. You should cancel your cruise. Your relatives won't cancel because the nephews want the water slide? Well, other ships have water slides. I shudder at the thought of adults letting the young ones dictate to them.
I doubt you'll have to worry about relatives seeing you through the glass. The glass doors are frosted and you have a curtain to pull across the whole area. You could solve your concerns also by moving to a suite.
The ship has plenty of entertainment. Yes, you can see Blue Man Group on land if you want to pay $100 per person. It is free on the Epic. Other free entertainment is Fat Cat's blues club which has an excellent band named Slam Allen. Legends, Second City Comedy Club, Howling at the Moon dueling pianos, and the Spice H20 adults only beach club with big screen on the aft lido. The casino is phenomenal on the Epic. There's also several other forms of music to listen to at the various bars and lounges.
Since you've destined yourself to stay in your cabin the whole cruise, you'll be happy to know they still have free room service 24 hours. Should you decide to explore a little you'll find they have several venues that are also free. The Taste dining room 534 seats, The Manhattan Room 598 seats, O'Sheehan's Irish Pub, Garden Cafe Buffet and extension Outdoor Grill, Spice H20 (Latin & Asian food), and the Atrium Cafe (light fare & snacks) all are complimentary. Pizza is free at the Garden Cafe, but you can request a pizza delivery anywhere on the ship for $5. There are plenty of complimentary eateries without having to eat in the speciality surcharge restaurants.
Cruising is all about choices and NCL Epic offers plenty.
Wow! You certainly do not seem to be looking forward to this vacation at all. I don't know why you'd want to continue with it? You're spending a lot of money to "show them" with your unhappiness. Did you really not know about the bathroom set up before you booked? I think that's the first thing I heard about the Epic - months before she was built.
I'm sure looking foward to my first trip on the Epic. And I'm also glad that those I'm sailing with are equally determined to have a wonderful time.
NCL Cruiser, sorry to hear that you'll have a bad time on your cruise. I can't wait to get on board the Epic. She'll be a very interesting ship to explore at the very least. The entertainment will be fantastic and I've always enjoyed the "free" food on board NCL ships. Sure hope they have those yummy sticky buns! If they don't, I know it won't ruin my cruise. I do hope Aunt Flo doesn't come to visit you, you can fix that problem if you'd like.