I simply see it as a lot of work. Every time you change cards, you need to consider the balance of the game, even if they're just minor changes.
If you want to apply this templating across the board, which would be "easiest", what if people start applying cost reductions to Elite Graboids? Then, they'd cost only 2 :Earth, and would be much easier to fit into speedbows, making the deck type even stronger.
And what about the cards that become noticably different cards? Puffer Fish? Archangel? By your method, we would lose access to those cards.