I have my doubts about this idea with not being able to set the costs I want. When I start a zerosim from scratch the bots can't have some costs at all because it whould whipe them out. Then as they evolve I can increase the costs and adapt them to what the bots can handle. this is very sensitive. Just setting the ageing cost to 0.001 instead of 0.0001 can whipe out the whole population.
Ideally, costs would be commenserate with morphological action, be it physical action or something else such as cognitive action. Zerobots would only be charged once they evolved to do something.
Just like today, zerobot evo sims need to have some nrg source that supplies bots some nrg passively until they evolve a means to feed themsleves. I use a veg nrg shot shooter to supply the sim with free nrg shots, but that is simply my being expedient. If we waited long enough, there are ways that bots would start aquiring nrg passively without it. For example, some bot would evolve to shoot -2 shots or -1 shots and randomly bump into veggies, creating nrg shots that other bots would evneutally absorb. Bots would die and decay into nrg shots, etc.
Don't worry. I'm very sensitive to the needs of zerobot sims and I totally agree we can't screw them.
I whould like to add why I'm so concerned about realism. It's because I see that DB can be a great model to try and learn how life works. For instance, maybe we can prove some day that life doesn't need a God to exist and that working cells can come alive and evolve all by themselves.
Your goal is a nobel one but I'm of the opinion that the route to virutal life does not necessitate exact imitation of biological realism and in fact may require intentional and substantal differences due to the different mediums.