I have Asuka so you can run a 2/6.25/2 attacker team with them :V
Freyr is an obvious pick. Dino or Beast Rider are good for heartbreaking if you have them. So is JoJoAres. ROdin is crazy good if you can get him.
Other viable subs are Phoenix( good RCV), Ulti Red Ripper, Flare Drall (also good RCV), King Flamie, and Red Samurai Goblin.
Also Echidna cause she's always good and synergizes with Freyr.