If energy (or, say, photons for plants) is introduced into a sim in the form of a constant drizzle of something like shots which start at the top of the screen, move directly downwards and give energy to the first bot they touch, that might encourage more interesting plant evolution. The current closest equivalent, pond mode, does not allow for "shadows" and tactics for stealing "light" from competitors. This way would encourage plants to grow upwards and outwards, and a multibot would have a definitive advantage over a singleton - a multibot could cover a larger area and grow into a taller structure than a singleton confined to rolling around the "floor". The problem I have always had with pond mode is that the lower regions are always so energy poor that if gravity is introduced the sim is so energy poor little happens. This way, even bots at the bottom of the screen get a decent energy input... as long as there's nothing above it.
This post was rushed because I'm about to leave work, but the idea behind it wasn't