Are you asking how agents should be created? Are you asking is uniqueness a problem? Do you want to maybe run the agent by the community and get input?

I will say this, I cannot specifically say as to agents, so my advice is more about characters in general. When I have a character I am having trouble with I take one of two approaches. I either scrap the character and start from scratch or I keep revising.

Lets look at this character you are having trouble with. I will use my own as an example. Right now I am still pre-writing my future agents, deciding what I like, what I don't, etc. One of them, Cipher-7, which I introduced in our semi-RP thread a little while ago, is pretty well set, I just need to finish out a few details with her. The second one, which is more in line with what seems to be your problem, as of now is named The Justicar and I really have nothing else to him. I just was not quite feeling the character, almost that the development would be artificial, unnatural. So the way I see it, I can use that character and keep revising.

For the Justicar, I had intended a Time Lord Agent. Lets say, I like the idea, but my initial version did not work. I might take his sense of fashion and background and start a new character from scratch. Or alternatively, I am unsatisfied with the character all together and scrap him. Start with something new. Different. Right now I am looking for something that is going to clash with Cipher-7. She is basically a strict by-the-book military type. She likes using range and strategy to take down an enemy, and is frankly a bit racist towards non-human species. So, if I want a good foil for her, I come up with something like this.

1)By the book: The character does not need to be undisciplined or a loose cannon, but maybe his book of strategy looks a bit different. Maybe his book says Attack! Attack! Attack! and Shoot First, don't ask questions. So there is a difference in discipline that will work well here.

2)Range and Strategy: Well here the clash would be someone who likes to get up close and personal and acts rather than thinking

3)Dislikes non-humans: Make the character a non-human.

Really what I am trying to say here is if you are at a lack for ideas, and you like your one future agent, then create a foil for it. In other words Cipher-7's foil would be either a Klingon or Krogan and both are from Science Fiction universes. And so now you already have a potential plot that the characters would drive.

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Alternatively what you could do, especially considering the nature of the PPC, is consider a type of character from one of the universes. Say you wanted a Tolkienverse Elf. You have a large chunk of the creation done, because of the requirements, range of abilities, appearances, etc. in the Canon. What would be done then, is build the character out from there.

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Additional Alternative

If you are going an original character route, then really my advice to you is start at the core. Find something you want, be it a name, a race, an ability, talent, etc. Use that as a kernel to build on. Look at it this way. I have a character, lets call it X for right now, all I know is that I want the character to be male. So now X is a man.

You can then ask yourself some questions about that character. Where is he from? Does he have any family? How old is he? What is his favorite food? Does he have a name? Things like that.

When stuck with any character you can always ask yourself questions. Have a metaphorical discussion with the character.

I hope that helps.