The 5250 data stream itself supports unicode...
The problem is that most 5250 terminal emulators do not. This include's IBM's own iAccess for Windows and Personal Communications...
The only 5250 emulator I'm aware of that supports uncode is IBM iAccess for Web.
http://www.think400.dk/files/Whats_with_these_ASCII_EBCDIC_Unicode_CCSIDs.pdf