The room doesn't have to be a "perfect" rectangle, so having 36 feet instead of 33 feet is not going to make much of a difference. I think I remember reading at some point that the "double-rectangle" is not the best solution. It seems to me that the best shape is more like a 50% longer length than width. So if your room is 16 feet wide, the length would preferably be something like 24 feet long. Don't take this as a hard recommendation because I don't know for sure. In actuality, smaller rooms have more bass problems because of the room nodes cancelling out bass frequencies. So a larger un-even room will help in this case.
That room, even at 16 feet wide, is considered a large room. I would make sure you had enough amplifier power as you will need a lot of watts or speaker efficiency to fill that room. Getting smaller 100 watt per channel amps should be avoided if possible.
I would recommend that you have the electrician use 10awg romex. Many will use the smaller 12awg romex, even for 20 amp circuits. I have heard others that like to use larger 8awg or 6awg wire, but everything at that size is going to be stranded wiring. 10awg romex is the largest solid-core solution. Just add as many direct circuits as you can. Use high grade audiophile outlets, such as Porter Port or PS Audio, or even Furutech rhodium (which is best in my opinion). VH Audio and Audio Sensibility are vendors that sell cryo-treated 10awg romex, if you want to go that far.
I wouldn't worry too much about the bay windows. You can probably get projector screens that have solid-black backing. Otherwise, you'll need light blocking material on the window behind the screen.
I don't think you need to black-out the entire room. In my opinion, the most critical is the wall that holds the screen. Most of that front wall should be blacked out. You can do this with curtain type material if you want. A small amount of the side walls can be blacked out to help (maybe 5-7 feet if you really want). The idea is to black-out the area around the screen so that your brain doesn't translate the "screen" as just a television. Blacking out the area around the screen will help your brain "perceive" only what is shown on the screen. Having a white/reflective area around the screen will distract your brain and you will lose the "immersive" effect of movies.
I would make sure the entire floor is carpeted (at a minimum). Then you can play with certain types of sound panels at different locations if you really want to.