2: Harry Potter's patronus is a stag.
3: James was staggeringly wealthy - the source of his fortune has never been fully explained.
4: One of his best friends was Remus, a werewolf
5: The sorting hat thought that Harry would make a good Slytherin.
6: Another name for a stag is "hart"
Putting these facts together, the conclusion is obvious, I think - James Potter was the heir to the vast Wolfram and Hart fortune, the human avatar of the Hart. For some reason he wanted nothing to do with the family business, and all of his income from the law firm was deposited in Gringrotts for Harry, who is now the avatar of the Hart. Remus probably isn't the Wolf, their association was more along the lines of an instinct on James' part. He never had a friend with Ram associations, there just wasn't anyone around with that particular animagus form or patronus.
Some obvious plots
1: During Angel S5 / post Half Blood Prince Harry becomes aware of the connection and decides to call in the debt the company owes him - not sure what form this debt takes - and have them take care of Voldemort and/or the Horcruxes.
2: Angel becomes aware that there is a living avatar of the Hart and decides to investigatge him.
3: Post Not Fade Away there is only one survivor, and Illyria wishes to do more violence. Taking out the human avatars of the Senior Partners is part of her plan...
I'm not going to write this, I think, but if someone else finds a use for the idea a credit would be nice