Basic Pokemon evolution substitute type card

Due to the deck building rules of having a max of 2 of the same Pokemon it makes it decks that have multiple Pokemon that evolve from the same basic Pokemon unviable or Impossible. For example there will soon(?) be Lucario, Lucario ex and Mega Lucario ex that will all require a Riolu to be played making a deck that gets all 3 of them into play impossible. My suggestion is to add either a fossil, substitute doll or Ditto card that can act the same as one of your existing basic Pokemon in play and be evolved allowing for players to build more decks based on split evolution or an ex and non ex evolution of a Pokemon.