Wow that sounds like a really neat way of doing it, I'd love to explore that shader workflow. I'll have to boot up Bioshock and give it a look! If we wanted to achieve some of the type of foliage we want, L-systems would certainly be a great way of achieving both variety between plants as well as a lot of controllable…
One way you could do this would be to create an animated shader that 'grows' leaves based off a control texture. I worked on the art for the plants in Bioshock that did exactly this. There was a texture with various grey levels for different leaves and then we animated the contrast on the texture to progressively display…