I have seen a couple of Arren's before, so I don't think it is incredibly far-fetched. I think it just looks like an alternate of
Aaron, an alternate that holds more meaning to you. I personally wouldn't use it because of the creative spelling, but I don't think it would be odd if you did. In the middle name slot you probably won't get questions about whether it is a creative spelling or not and you won't have to constantly spell it out for people.
Were you thinking of using it on a girl or a boy?