OK, I'll grant that I don't get the compile-time attribute safety and thus this isn't really "inside-out" in the full sense of the word. However, it's not an XY problem because the specific problems that I deal with over and over again are twofold: one, people constantly violate encapsulation. Two, the compile-time safety isn't much of an issue for me because I write enough tests for my code (caveat: when working in a sane environment), that I catch the bugs up front.

Further, the syntax of various inside-out object modules is just frickin' painful to me and I've used them and tried to evangelize them! When I try to get others to used them, I invariably get a huge amount of resistance along the lines of "blessed hashes are good enough for me". Regardless of whether or not it's rational, when you're on a team of five programmers and the other four agree with the concept but flat-out reject the implementations, you have to know when to cut your losses.

For me, it's the encapsulation which is my biggest concern. If I can provide a way that programmers won't violate encapsulation but it's very easy for to migrate to (with sane code, nothing breaks!), then I've solved the exact problem I'm faced with. If you're trying to solve a different problem, then the XY problem applies.