Not sure if people want this but thought I would post this anyway just in case. As the series goes on I will add more and may even add some fan suggestions.
Card changes:
Valhalla, Hall of the Fallen: Once per turn, during your main phase you can special summon one Fairy type monster from your hand in attack mode.
Koitsu: Once per turn, during your Main Phase, if you control this card on the field, you can equip it to an "itsu" monster as an Equip Spell Card, OR unequip the Union equipment and Special Summon this card in face-up Attack Position. While equipped to a monster by this card's effect, increase the ATK of the equipped monster by 3000 points. When it attacks with an ATK that is higher than the DEF of a Defense Position monster, inflict the difference as Battle Damage to your opponent's Life Points. (1 monster can only be equipped with 1 Union Monster at a time. If the equipped monster is destroyed as a result of battle, destroy this card instead.)
Doitsu: Once per turn, you can equip this card to an "itsu" monster you control, OR unequip it to Special Summon this card in face-up Attack Position. When equipped to a monster by this card's effect, that monster gains 2500 ATK. (A monster can only be equipped with 1 Union Monster at a time. If the equipped monster would be destroyed by battle, destroy this card instead.)
Draw Muscle: Target 1 Defense Position monster you control with 1000 or less DEF; draw 1 card, also that monster cannot be destroyed by battle this turn and you take no battle damage from any battles involving that monster. You can only activate 1 "Draw Muscle" per turn.
Mirage Dragon: Your opponent cannot activate Trap or Spell Cards during the Battle Phase.
Flash Fusion: Fusion Summon 1 Fusion Monster from your Extra Deck, by banishing monsters from your field or graveyard as fusion material. Destroy it during the End Phase.
Ring of Destruction: During your opponent's turn: Target 1 face-up monster your opponent controls; destroy that face-up monster, and if you do, take damage equal to its original ATK, then inflict damage to your opponent, equal to the damage you took. You can only activate 1 "Ring of Destruction" per turn.
Amulet of Ambition: Equip only to a Normal Monster. If it battles a monster with a higher Level, the equipped monster gains 1000 ATK x the difference in Levels, during that damage calculation only.
Custom cards:
Double Recall: Target one level four or lower monster in your graveyard, special summon that target in attack mode and double its attack points. During the end phase of your opponents turn destroy this monster.
Soul Cannon: Target one monster you control and equip this card to it. The equipped monster can only attack by tributing a monster from anywhere on the field. You can tribute multiple times with this effect.
Redo: If a monster is destroyed by battle, you can target that monster in the graveyard, special summon it to its owners field and double its attack points. If a monster is destroyed by card effect, you can remove this card from play from your graveyard, special summon that monster and double its attack points. You can only use one effect of Redo per turn.
Goitsu: Special summon one 'Itsu' Union monster from your deck and equip it onto an 'Itsu' monster. Also attach this card to the same monster, the equipped monster gains this effect: Gains attack equal to the total monster cards in both players graveyard x300.
Equip Revival: Target one equip card in your graveyard and equip it to a monster on the field. The equipped monster cannot attack while it is equipped with the equip card.