another follow up:
I connected a usb2 ext. HD to the Airport Extr Basest. (AEBS) with iTunes library installed (applelossless, wav,aiff,aac) and movies (m4v,mp4) .
For playing music from the iTunes library 2 possibilitys ,
1. iTunes match through AppleTV and iPad is a very nice solution having the library available without an active Mac but no lossless or any HDmusic available (max streaming 256kb/s).
2. So for audio in lossless,wav or aiff the music can be streamed directly from the AEBS connected drive using een app on the ipad like "Remote File"
For movies I use this "Remote File" app on the iPad which allows access to all files on the usb drive.
Movies or music can be started by double clicking the file , ofcourse without any iTunes library items (metadata) , and up to now no problem encountered with HD movies freezing .
(and uploading movies in iTunes match seems still limited to 15minutes film at the moment ) .
Backup solution could be a Raid HDD , but that's the next step i intend to take.