>  Does it require a complete new snapshot, or even two of them?

the problem is, that the last binary NetBSD/Amiga snapshot was from 1.2D
times, some weeks before the 1.2E change was done.

The code is now integrated into the kernel sources as of late 1.2G... 
That is, at least 3 important kernel/kernel or kernel/userland
interfaces have changed.

I don't recommend building mixed kernels, and you'd need at least a new
swapctl/swapon command with new kernels, and new libkvm, among other
things which I don't remember.

People which betatest -current and do frequent updates might be able to
provide others with binaries, or even build at least binary tarballs
(the makefile rules are all there).

	-is