[da-anda]

Put every DVD, add it to a library and than XBMC will say - you have to put disc labeled 'TJERRY002_CZ' (which is a label on original Tom&Jerry DVD) in order to play this item?

I think technical there is no other way from within XBMC to index "physical" movies - the removable media has to be available to the pc. What could "ease" things up for you might be some external tool that's pulling your ANT or whatever movie library into XBMCs library - but you will there also need the correct label name.

Another way would be the fake movie folder stuff as SPIFF suggested it, but that's about the same workload as you have to write the volume label by hand in the nfo file and therefore most likely have to insert the DVD anyway. But the advantage would be that if your DB is broken you still have the folder structure you can reindex.
But apart from the usecase for DVDs/Discs, storing the volume label is also highly useful for any other removable media like USB-Sticks, USB-HDDs and memory cards - although the possibilitiy for custom labels (additionally to the real label) could be taken into account.

So maybe both approaches (volume label and fake folders) are together the overall solution for offline media in general (be it discs, cards, hdds, etc)

I'm not sure, but I think there might be something similar to CDDB for movie DVDs on the net where XBMC could grab the "humanified" label of the CD/DVD? Does anybody know something?