Well implementing ARM-FFI is largely orthogonal to Athens.Yes, i am happily using it for Cairo and it lets me customize /rethink things as they gowithout need to touch VM. Which means much faster development process and feedback etc.But since Athens API is settled down more or less, now it is quite possible to implement a pluginfor different backend, knowing that it won't require huge changes later.
Concerning ARM:- Damien Pollet works on ARM assembler for ASMJit.as soon as it working, we can try doing something with it.But in addition, what i would like to do is to move more towards platform-neutral FFI implementation,
using low-level assembler DSL which is platform neutral. There's a work started on itas part of Mate project, but it is yet far from finished.