Don't forget that there are more seasons to come. Plenty of time to see different characters in action. He may be in season 2 or 3 or what ever, you'll just have to wait.
yeah, they have already been showing some new clone stuff for season 2. the production folks brought an eFX helmet painted up in wolfe's new design to a con recently.
There's a petition going to try and get the RC's in the series. The link is in my signature. Not sure if it will make a difference but I think it's worth a shot!
I would love to see the ARCs and the RCs in there as well. As for Commander Keller's appearance, I don't think he has appeared yet. If you're thinking of the one episode on Pantora, the only clone named at all was Rex. Commander Keller's Wookieepedia entry only has him listed as appearing in Star Wars Republic: Into The Unkown.