My personal take on the whole 'we need a new alternate AmigaOS thing' is that we don't and we won't get one even if we did.
The whole concept of an OS in the traditional AmigaOS sense is fast becoming obsolete!
Instead I'd like to focus on something more achievable...bug fixing and improving 68K OS 3.x so we could use it on our Classic hardware and emulators (as a hobby!).
A real-world example of what can be achieved is Peter K's excellent ICON library replacement
Ideally you'd take the old 68k assembler code and refactor it to plain C, this is needed because there aren't many of the old assembler guys around (this is what Hyperion did with the old 3.1 code to build OS4). After refactoring the code you'd open-source it so that the community could work together to improve it.
The other option would be to simply use AROS 68k and put the effort into making it run efficiently on real Classic hardware.
With the development of fast FPGA stand-alone boards and accelerators it looks like there is plenty of life left in 68k land
We could even back-port some of the features/improvements introduced into OS4 so it would't have been a wasted effort