Thanks for your feedback! I see you would like to make the creation of creatures simpler, but changing it this way may result in some issues.
Creature’s skeleton, muscles and fat would be generated and altered by the player to some degree. Removing these options and replacing them with pre-made parts would restrict the creativity of what can be made.
I agree about the organ part, every single one doesn’t have to be designed but there still should be options for how some of them work.
Senses that humans don’t have are definitely planned for creatures.
With male and female dominance it’s a bit more complicated. We can’t assume that every alien creature will have the same sexes as animals on earth. Of course the player would be able to implement males and females but the options for various other ways of reproducion should be available too. The feature for making different variants of the same species is planned and the integration between them could be more complex than just domination of one.
Plagues and toxins sound good and they probably will be a feature, though we can’t tell how complex we can make it to be.
And lastly, unlocking various items is a very restricting way of allowing a player to evolve. Biomes that the player is in should not remove the possibilities of which animals can adapt to them because every feature can be used differently. The most organic way is to change part’s specialization overtime. For example fins on a desert could turn into a cooling fan just like ears of fennec foxes on earth.