Hi Vodun! :)
For the card game:
Since the remaster is based on Legion Saga III Version 3 (which the Cardico mini-game was fully playable), yes! I will probably redo it from scratch, but even without touching it, the mini-game can work as is. ;)
For the Unite Attacks:
I am not sure yet. Adding custom mechanics into the Rpg Maker 2000 battle system has always been a bit tricky. But I do intend to take a closer look at it (I also wanted to create a Sunbeam Orb that heals the character at the end of each turn, so we will see).