I don't think OOO used the ballad version of the opening for the preview either. I think it was also generic sad music.
Yes.
In OOO, The ballad version of "Anything Goes" was used during a dramatic scene (in a bridge, I think. The one usually used in Toku Shows. I forgot) between Eiji, Hina, and Ankh.
Now in Fourze, A slow, instrumental version of "Switch On!" was used during the dramatic scene of Gentaro, Yuuki, and Kengo in JAXA.
I think that scene in OOO was about parting each other which also was did by Fourze in the latest episode.
Come to think of it, W never had that same interaction between Akiko(show heroine), Philip, and Shotaro. It was only between Philip and Shotaro with an acoustic rendition of "Cyclone Effect" playing in the background (parting between partners as well)