Correct, character-type parameters for UDFs are supported as of SPS 8.
I thought the cloud version would be on SPS 8 by now - but apparently it's not 
I see the use case, but there's currently no string-unpacking data type conversion available, except for date/time data types.
About the partitioning: what exactly do you want to do?
Distribute data evenly into table partitions?
Partition type HASH does that already automatically.
- Lars