Yeah, I've seen kits that can be used to add that longer line to an existing slave cylinder. I intend to get one installed when I get a new clutch installed in the C5Z. Can't really figure out why GM has it set up the way it is stock. I don't know how you could actually bleed the clutch fluid lines without something like that.
http://www.tickperformance.com/tick-...-firebird-ls1/
This procedure in the video will work in a pinch, I guess, but still not as good as doing an actual flush to quickly and completely remove the old fluid and replace it with new.
I did this one on the C5Z, and I guess it's probably due to be done again. Probably should take a look at the C6Z too, while I am at it.