Putting some new cards in the starter decks is a good idea.
But, I don't know why having 6 pairings instead of 12 is a big deal, as there's no synergy in the said pairings (except for the current Air-Light, or here Fire-Water). Often, players will get rid of the off-element cards until they can build some new ones.
Having off-element cards is a good idea, as it helps to discover synergies between elements, but why choose these 12 specific pairings among the 132 possible ones ? We can imagine that the player chooses his/her primary element and receives a random off-element, or chooses both, etc.
If I remember correctly, the starter decks were already like this since before the free Metamorphosis. Now we can even think of starter deck with a different mark than the element chosen. The starter decks just have to be... poor, while helping the new player discovering the different play styles of the elements.