Very good game. Few reccomendations:
1. Able to challenge your friends or people through room chat.
2.Private matches (password or soemthing)
3.More cards ;P
4.Able to swap the resistances (light, dark, physical..) to create more versitility and specific decks.
5.Specialist matches (x-type charectors only to give added strength to charectors)
6.Level specific rooms to allow new players to find decent challenges more easily
That's about all i can think of now but great game and will maybe add some more ideas later xD