This would be helpful - especially so if they're useful to the herbivores. Though I would definitely want varieties within each type. One of the things I find myself fighting a lot of with the last foliage update is repetition creeping up in my designs. I love going nuts with foliage though. Absolutely love it. I spent last night designing a t rex enclosure entrance - not the actual enclosure, just the entrance - it took me 4 hours, 3.5 of those hours was foliage.