See if I can answer some stuff here.
1. It doesn't take much room at all to transport my stuff. I've done really basic designs and themes so the largest thing I've transported is a small plush. (and I've since bought the teeny tiny TsumTsums so even smaller). The most room I ever took was over mardi gras because I had a ton of beads and about 5 half masks (paper) and 2 small plushes. It all fit in a small packit cube.
2. I see it much more at the Values but I've done and seen it done at the moderates as well, just not as much. Usually see 4 or 5 per trip in my building. Trips around Halloween have more (and I would assume Thanksgiving/Christmas/Easter may see an upswing as well).
3. I'm staying at BWPPI so I don't know if the windows look out on the walk ways or out towards the edges of the property. I also don't know if the windows have a sill inside to set the toys on.
4. Housekeeping is my worry. I've never seen anything about Housekeeping stealing the window displays, but it's common practice at WDW. My current Window items are trading pins and the above mentioned TsumTsums so they could be a little more appealing to snag. Which I know is probably paranoid. I believe that 99% of the time housekeeping would not steal. I've stayed in enough hotel/motels to know that I've only lost one item in my life which was partly my fault so the chances of anything going awol is small. But some of those pins are not easily replaceable.
5. I think I may pick up some inexpensive stuff this weekend (clings or small dollar tree type stuff) and supplement with some publisher sheets and do just a small job of it. I'll leave the pins at home, since they represent the biggest $ investment.
I'll upload a picture of my window at AllStar Movies from Janurary. It's the beginning stages of my current Decorations.
I plan to add some more to this but all of that fit in two quart ziplocks. That window faces outward to the walk way. A few years ago I was at PORiverside and I faced the courtyard where the movies were shown and the walkway to the main path so I had tons of kids looking at my window and calling it the mickey window (I was using the small Mickey and Minney plushes plus some LGMH's from Home Depot to spell out a birthday message, so it was very much Mickey centered.