FireWire is unfortunately on its way out, despite its technological advantages (e. g. that FireWire 2.5" drives just work and better performance), but c'est la vie.
I was in a local Mac store (big chain in Germany, actually), and they had exactly no enclosure that could power itself down. Ditto for the best computer store in town for parts. It's a big gripe, because I have to switch one of the drives off manually (my external drives are hidden behind my printer).