Beyond that, I'm not sure if buying Be would have fixed the managerial problems at Apple. Would they have been able to add the required features to BeOS to turn it into a production OS without the project turning into another Copland? Would the existing Apple management have slimmed down the massive Apple product line that had dozens of nearly identical models? Would it have gotten rid of dead-end projects like Newton and Pippin? Etc.
Jobs is what makes or breaks Apple in that critical period. I didn't like him but that's relevant to the success of the company. JLG did not have whatever it was Jobs gave the company.
32-bit Haiku can run old Be apps, but must be built with ancient GCC.
64-bit Haiku is built with modern GCC but it is not binary compatible with old BeOS.
This is a surprising amount of effort to not break compatibility ;-)
We paid Cygnus(?) millions for that. The multiple virtual inheritance needed for MediaKit was a real joy to get working.
https://www.youtube.com/@designedinca
(Specifically they talk about Be beginning: https://youtu.be/5IFxwnXASyQ)
If not, desktop computing would be taken over by C++ as main systems programming language, and UNIX like computing relegated to servers.
In the places where there's something entirely different going on, such as networking in earlier BeOS, it's trash and you'd obviously want to throw it away and do what Unix did - Be were doing so. So a hypothetical turn of the century fruit-flavour BeOS is probably much closer to "Unix with a different UI" than you're thinking. NeXT changed nothing there.
The amount of work done by Haiku to provide a proper POSIX userspace support proves the point.
1. The Rhapsody developer previews, which are NeXTstep with a menu bar at the top and desktop icons, and a Platinum skin.
2. Mac OS X Server 1.x which has cascading finder windows, an icon view by default, and some other things much like that.
3. Mac OS X 10.0, which I used, or tried to use, as a daily driver, with a broadly Mac-like experience with an Apple menu, but with app names next to it containing global "about" and "quit" options, and so on.
It never did acquire any of the nice stuff that came in with System 7 (e.g. drag-and-drop customisable Apple menu stored in folders in the System Folder) or MacOS 8 (e.g. folder drawers that shrink to tabs).