I don't know what's going on here? UNIX' directory structure was adopted back in the days of DOS version 2.
You're smarter than that and know what I mean, without having to require users to always be technically accurate. This is not an Unix forum, while perhaps appriciating a more accurate report of both Unix and the history of MS-DOS. If I want an Unix directory structure with an own root, including but not limited to solutions like RPM, then I'll start using Unix. I won't.
Every OS/2 system has an "Unix directory structure" even when IPLed from floppy or network. And for sure every user who's posting here from an OS/2 (or NT) networked station is also using a BSD-derived IP stack. It's not a good idea to mix different topics namely directory structure, file system and UNIX. Only a simple example/question for porting trivial stuff: How about a shell script that handles "compress"ed UNIX files *.Z and also "pack"ed UNIX files *.z?
I could have installed such a (full) structure while smiling and not noticing it, while installing eCS 2.x DE/EN or AOS EN. But DE nor EN still isn't the prefered foreign language of the OS over here, and the developers of eCs 2.x and/or couldn't be arsed to produce an official directory structure-related upgrade for OS/2 and eCS. Different products, smaller user base. Most of the non-DE/EN community of IBM's has already left us, often without telling us.
For economical reasons only German counts for large remaining OS/2 deployments. There were two groups of people in the U.S. forced to learn German: DEA's dog handlers and IBM's OS/2 kernel developers.

Thanks for explsainig what Mensys did, but it's quite obvious that resources are limited. The reduced number of eCS 1.x and 2.x languages, compared to Warp 4 FixPaxk 0, has reduced the size of the community too.
Warp 4 fixpak 0 (XR_M000) was only available in American language AFAIK. No convincing argument.
That's nothing but a fact. Of life. I'm not demanding all files in one directory, but I'm often pointing out that such a change can, and should be avoided. FF45 is just an example of an important product "we" aren't using anymore, and so is an updated silly Qt-based game or most of the un-OS/2'ified GCC port. If I want most of Unix, then I'll start using Unix.
It's not fair to blame Unix for the chaotic YUM/RPM situation under OS/2-based systems. The current partly ported RPM features (from an quite outdated release) unfortunately leads to misconceptions in this area. Unix is about small tools that make a great environment. The GNUish bloatware around is not UNIX. To make it clear I don't want to blame FSF here. And so-called open source software existed even before. There are quite good examples for portable software. But also wrong assumptions which will cause trouble under OS/2 targets sometimes torturing end-users with wrong documentation, non-working national language support or other issues. It's a effortless regurgitation to write bug reports for recurrent disturbances.
I welcome every cooperative approach to extend the coexistence of portable software. Unfortunately some people spreading rumours here seem to have their own economic interests. That's not a bad thing at all ...but there's also a category marketplace in this fora most suiteable for mountebanks.