I've planned out how I'm going to do the 2nd of the 7 tasks I need to complete, and I should finish it tomorrow. I just needed to be careful thinking it out. What I'm doing now is putting in the framework for creature groupings (hooved mammals or rabbits for instance). For this I need to make structures (clades) that bias the mammal generator (e.g. so that the hooved mammal clade always produces a mammal with hooves -- rabbits would bias the mammal generator to produce smallish mammals with certain features, such as the distinctive ears). This way, I just specify what it is to be a rabbit relative to other mammals, and then the mammal generator can spit out 4 billion distinct types of rabbit with no further effort on my part. This is basically the same way I currently make items (an item is a list of restrictions on what the item can look like and be made out of).
I wanted to do this before I made the editors to avoid adding all of this material to the editor interface at a later time and also to prepare for the ecosystem/vegetation release -- ecosystems will be much more interesting if there are different groupings of creatures. These things will also allow you to create entire classes of creatures within a given motif (e.g. "mammals"), instead of just working on specific stock creatures.
I'm also going to add in caste alterations, so that human males can be made from human females with minimal effort (that way, they'll look mostly the same, as they should).
I think for the species editor there will be at least two different modes. One will allow you to specify a creature entirely, and the other will let you fill out a simple form that determines the creature's clade (creature grouping) and some specific characteristics (size, eating habits, intelligence level, etc.). That way you can get roughly what you want without all of the effort. You'll be able to vary the seed explicitly so you can keep trying until you get something that looks about right, and if you'd like to transfer to the other mode to make some final modifications, you'll be able to do that too. This will probably be the best way to do things (unless you're making something really messed up), because building things up from scratch will be Quite a chore. Just go into the status screen and look at a description of your species to see what you'll be up against.
Any suggestions for what material/form/species/motif/clade editors might be like should be made soon, since I'll be starting them shortly.
I'll also be reading about the deformation theorem for flat chains.