At any rate, we'd love to at least have your patchset in HaikuPorts, even if it's not quite ready for prime-time yet.
However if mmap is more significantly broken then Haiku needs work - Wine does need the ability to map things into the address space at the requested locations and actually get it.
mmap on a fixed address should work just fine, unless the address is outside the normal range or in an already mapped region, which seems to be a problem on 32-bit systems. I think there are some emulators we have ports of which already use MAP_FIXED quite a bit.
Nit picking comment aside, I wonder if the fact that it is single-user was one of the reasons Apple did not go with it.
The beauty of each desktop centric OS is the whole platform, the set of SDK languages, the respective frameworks for exposing the OS and hardware features that make the desktop experience unique, and IDE developer experience.
If it is to run desktop agnostic apps, then anything can do.
Unix had it different with there being no core experience in the first place -- X11 being a glorified terminal multiplexer plus xeyes. Whether it was the commercial Unices with OpenLook/NeWS vs Motif/CDE or later Linux with Qt vs Gtk. Not that there wasn't a chance -- at one time Motif won over the commercial sector and if it would've been available with the same license as Xlib/Xt, GTK would've never been developed.
But that seems to be a thing of the past. These days the web forced us to give up all platform-specific UI expectations -- heck, any expectations of having a proper UI in the first place. And thus applications are all over the place, Electron being just one particularly heinous culprit. Material UI on the desktop. Plenty of applications starting up web-based interfaces in the browser.
On the one hand, as you say, this doesn't make the particular desktop matter anymore, it's more a vehicle of getting your wifi driver to work properly and load the browser. So one could use Linux or even Haiku without any big losses. On the other hand, if everything's pastel-colored oatmeal, there's no big benefit from a neat, unified, C++ desktop experience that BeOS was aiming for.
If you want a vision of the future, imagine HTML stomping on your face -- forever.
I don't need such vision, it is how it would look like if all OSes happen to jungle browser instances, ChromeOS style, while a big chunk of applications runs on someone else's computer, abstracted via language runtimes.
The return to mainframe's timesharing days and very sad outcome for desktop computers, with the minimum experience common to all vendors.
Graphical APIs not able to take advantage of hardware, hardware support that takes years to have minimal APIs, drawing UIs pilling divs customized with CSS and JS to mimic visual behaviours.
The reason apps all went cross platform is that desktop operating systems stopped innovating. Which is the desktop platform with the most new native apps, where developers take pride in making non-cross platform experiences? MacOS for sure. Which desktop OS has been consistently the most innovative over the past 20 years? MacOS!
Haiku running IntelliJ is technically interesting, but ultimately as a user I don't understand why I'd want to use Haiku. BeOS may have been innovative 20 years ago but it's a dead OS that hasn't changed in decades. May as well run IntelliJ on any other platform, then.
I think the desktop can be great again, but it will take a new generation of developers with new ideas about where to take operating system technology. I also tend to think that whoever tackles that problem will probably tackle it by writing a cross-platform app runtime that slowly expands to become more and more of an operating system until the actual OS is indeed, just relegated to providing some drivers and bootstrap code. But the actual UX will be defined entirely by that environment. Sort of like how Pharo gives you a full blown desktop environment when you start it (but I'm not arguing for Smalltalk)..