With my new collection of settings, you can force only vegys to have and evolve chloroplasts and nothing else. So that is a minimum threat.
For people who like to see ecosystems with chloroplasts evolve, I am running experiments right now myself, and it is looking pretty balanced. It just takes a while as the whole screen must be saturated.
For people who are worried about robots with chloroplasts causing the leagues to run 4ever, there is already a rule to timeout the league.
So really, new users will not have anything to worry about.