I have played diamond more hours than I care to admit when I was really into online play. I just recently got a second copy of diamond and the nostalgia is taking over. I have made everything from a noob team to competitive and challenge runs, but now I am totally nerding out and making a team based off of the characters that do double battles with you in the game.
So off the top of my head I remember Dawn, Barry, Cheryl, and Riley doing doubles with you. I might be missing someone. So the team I am shooting for is going to be:
Lucario, Blissey, Roserade, Rapidash, Floatzel, and Alakazam.
Lucario as the egg from Riley.
Blissey as the Happiny egg in Hearthome to emulate Cheryl.
Alakazam as the Kadabra that Dawn uses.
Roserade, Rapidash, and Floatzel as the choices Barry takes based off of your starter type.
I don't plan on using my starter and I will just use a random Staraptor to fly. It will be a pain in the butt to make this team but I really have done everything else.