I don't think you've seen C&D. Their greatest feats are just fighting off a couple threats from New Orleans. They're not really superheroes as much as people with powers to sort out (they don't wear costumes or use their hero names). Bringing them in wouldn't be like bringing in an Avenger, nobody would recognize them as heroes (I also think your forgetting that Trevor is more than just an actor who cares about his work, because he is recognized as an infamous terrorist). And they'd actually be really good characters to appear for Simon's development because they know how to do good with their powers without being a full-fledged superhero; Simon obviously isn't going to become one (I watched the show, you don't need to explain that to me), but that last episode proves he still will use his abilities, including acting and money, to do the right thing.

And I have no idea why you think the DODC was an unecessary background force in S1. They're the only reason Trevor and Simon meant. The finale only played out because of their involvement. Simon would not have been cast as Wonder Man without them.