Make less things hard-coded in texture packs!

Now, understandably not every block should have the ability to be see-through for obvious reasons. But, a lot of things are hard-coded that I feel aren't super important! Some that come to mind are birch leaf color, lily pad color, and the ability to biome-tint a block. All of these things are impossible to change without outside mods, and I feel that the technical community would really this, as with Minecraft being designed as a sandbox game, unnecessary limits are pretty aggravating. Thanks!