Dude, you're pretty new to 3D aren't you? You don't fucking use a bump or normal map for grass if you're making an animation. Maybe you'll use it for the base layer of grass in a video game, but that's about it. Rendering a field of glass is definitely not a pain in the ass, not any more so than rendering a bundle of hair really. Know why? Because the hundreds of thousands if not millions of grass blades are generally instanced, and thus don't incur much memory usage and are very quick to calculate operations on. And unbiased renderer couldn't give a shit how many grass blades there are, it mainly only cares about how many bounces you want to do and at what resolution.