Well, I think we should stay with MUI delivered in MorphOS to keep things simple, consistent and not to depend on too many software providers. It would complicate the process a lot. Also I consider AROS as a research system, always in development, not designed for usual end-user. I think Ambient is already open source but MUI could be still a proprietary and maybe author woludn't like to contribute in this project, then Zune could be a way to go.