all that needs to be done is the parser is there for only the player to see. It's totally private, and they can choose to turn it on or not.

None of the current rules in regards to DPS meters need to change. It's still harrassment if you read someone else's numbers, or demand a certain DPS out of party members, or expect people to reveal their numbers to you etc.
No mentioning it when looking for PF members. Basically, your DPS numbers just isn't anyone else's business. End of story.

People who'd like to use it as a tool get to do so, and everyone else can mind their own beeswax.