Yea, I thought that as well when I was naive FCP user.
Seems you need a workaround. Open your tga sequence in QTpro and export a high quality (animation or uncompressed codec) QT mov – make sure you use ‘millions of colours+’ to keep your alpha then use that in FCP. Lame eh?
At least there’s no level change between your ani_0000.tga and the resulting mov.
I’m only using FCP5.0 so they may have improved this.
Alan