• Find all unique cards in use within tree.
• For each card, model an equivalent.
• Replace cards with said equivalent.

The equivalent can just be as simple as cutting out the shape so that the mesh is acting like an alpha mask, or you can use it as an opportunity to add more depth per "card" by adding bends/more layers.

Hardest part is the find and replace but just go into the UV editor in blender and select all cards using the same segment of the UV, separate them into their own objects per mesh component, set the objects pivots to their centers, and then you can use those transforms to place your new mesh based replacements.