Hi Vijay,
Best approach would be as follows
1) Perform Unicode conversion and database upgrade together using OSDB migration approach
Export the source 4.6C on AIX 6.1 DB2 9.5 NUC
Build the target 4.6C on AIX 6.1 DB2 9.7 UC
Import the source database into Target system using R3load process.
Note : You need to execute the steps required for Unicode conversion during this migration
2) Perform Upgrade to ECC 6.0 EHP6 on target system
For reducing the downtime you may think of increase the CPU count on source as well as target system or use distribution monitor increase the number of parallel R3load processes during migration.
Hope this helps.
Regards,
Deepak Kori