I understand what you wrote, at the same time there won't be any super-powered creatures, that's why I wrote about hierarchy. 
There won't be the best creature or the most powerful creature in the game, that's generic, even you can say it became "normal", but to make something innovative one need to forgot everything that was used in the past and create something totally new, out of standards.
So if it comes to creatures, every will have it's own abilities that give advantage against some other creatures, some will be great workers also, some could fight much better than others wearing specific equipment or in specific conditions, some could have abilities unique only to them (let's call it signature abillities), some could fight better when being drunk or could reflect someone's fireball with double damage, etc. I could mention many things that says - yes, this creature for my actual needs, resources I have, enemy I know would be perfect to realize my plan of conquering this realm, so let's make it.
To sum it up there will be creatures the best in certain conditions, but not as ultimate monsters, so you could replace weaker with them. Stronger, weaker, there won't be such a thing like this and so we don't need to balance creature production cost, but their upkeep. " I was speaking in terms of total resource consumption per all members of a race. For example, 30 orcs could consume less food then 6 cyclotaurs, even though 1 cyclotaur would consume more food then 1 orc." - and that's good thinking, one of the way of balancing creature upkeep if we want have it with us happy and useful.
There won't be the best creature or the most powerful creature in the game, that's generic, even you can say it became "normal", but to make something innovative one need to forgot everything that was used in the past and create something totally new, out of standards.
So if it comes to creatures, every will have it's own abilities that give advantage against some other creatures, some will be great workers also, some could fight much better than others wearing specific equipment or in specific conditions, some could have abilities unique only to them (let's call it signature abillities), some could fight better when being drunk or could reflect someone's fireball with double damage, etc. I could mention many things that says - yes, this creature for my actual needs, resources I have, enemy I know would be perfect to realize my plan of conquering this realm, so let's make it.
To sum it up there will be creatures the best in certain conditions, but not as ultimate monsters, so you could replace weaker with them. Stronger, weaker, there won't be such a thing like this and so we don't need to balance creature production cost, but their upkeep. " I was speaking in terms of total resource consumption per all members of a race. For example, 30 orcs could consume less food then 6 cyclotaurs, even though 1 cyclotaur would consume more food then 1 orc." - and that's good thinking, one of the way of balancing creature upkeep if we want have it with us happy and useful.
Spec: Win 10, ATI 7800 HD, res: 1280x1024x75. I support The Venus Project & Resource-Based Economy