This is a cool mod that we've seen from a few people within the Casita community. If you have a newer Casita with the frosted glass door window, you can easily replace it with a window unit that contains integrated shades. This lets you see through the window and get sunlight when you want it, then close the shades for privacy at night.
We haven't done this mod ourselves, but users that have report that it is an easy installation. The new window is a drop-in replacement for the original. You just have to unscrew the original frame and put the new one in (probably with some outdoor sealing caulk).
Jessie Lopez of the "Travel like no one else" blog recently performed the swap and it looks great. They used this Lippert Components 806621 Thin Shade Complete Window Kit.
This is possible because Casita uses many off-the-shelf RV parts. For example, the refrigerator vent covers are standard Dometic units (more info on replacing that here). In this case, both the door and the window opening are common in the RV world and don't require custom parts.
Have you performed this mod? What window replacement did you use? How do you like it? Let us know in the comments!