By a "while" I mean three years... But I've stopped playing Minecraft then came back to it very recently (as in two-months-ago after being gone for a year or maybe more recently), and I've finally decided to throw my idea out here.
The mod will be called something along the lines of "Mystic Flora". Why? Because it adds magical plants to Minecraft. So far I've got only a couple planned...
Moonlace - A rare silver flower that can only be planted at night and is slightly more efficient than a sea lantern.
Sundrop - An equally rare flower that also provides light; can be used to heal players or zombie villagers; one flower can be used up to five times before being consumed.
Crystal Flower - A rare underground flower that can be crafted into diamond or emerald, depending on the colour (blue/green)
Charcoal - Natural blocks of charcoal which will mostly be found in deserts or any biome with a lot of plant material, but underground.
Seed Plant - A plant that can be harvested to provide "Raw Seeds", which can't be cooked.
Plant Cloner - An item that has to be placed in the world, it turns raw seeds into plant material, the amount of seeds differs depending on the plant; vanilla plants (cactus, flowers, mushrooms, and saplings) take a small amount of seeds, while things like moonlace, sundrops, and crystal flowers require larger amounts to multiply the plant in question.
I don't necessarily to actually make this mod, but it's just a concept I've had and I thought that maybe I should share it with the public. If I do actually get to make this a mod, I'd maybe like to include some sort of carnivorous plants as well, trees, decorations, etc.. But for now, it has to remain simple and not overthought.