You can set the "Remote Owner" attribute to the user you want to own the files in HDFS. You can set "Remote Group" as well. Both of these are at the processor level and do not support Expression Language, so you'd have to set them for the processor. You could use a RouteOnAttribute processor to determine which user should own the files in HDFS and route the flow to the proper PutHDFS processor, but this will be more cumbersome than distributing keytabs to the users.
In a secure environment, the users would likely need to have their keytab to write to HDFS anyway since you'd have to authenticate somehow and there's not a way presently to pass a Kerberos ticket to NiFi.