But what about all those other horrible non-RPM distributions? What should they do?

The "ecosystem" isn't fragmented as it is, unless you're talking about a lazy proprietary developer (the ones that whine loudest about the kernel's dynamic nature, for instance) that insists on everyone conforming to their desires.

About the only way to eliminate this "fragmentation" of which you speak (you may be confusing it for diversity) would be to forcibly shut down every distro outside the one you prefer, since even openSuSE and Fedora differ in ways such that packages don't migrate cleanly.

Yet despite Linux's dynamic nature, some companies, like Xilinx, still deliver their most powerful software in a manner that works on more Linux systems than just RHEL or SuSE Enterprise.

I suppose you are suggesting that this would allow developers to generate their own packages. There's nothing stopping them now, and they'd still have to generate multiple RPM packages, one for each distro in question.

Yes, because the MeeGo standard explicitly states compliance to the LSB and the LSB specifies using RPM. That, however, is only a tiny issue with respect to why Maemo 6 does not qualify for the MeeGo name.