The properties you see in the screenshots are not just shown, they are fully editable via command line and gui. Cubit can be run headless afterall. So the gui is just here to help creating commands. The commands are usually journaled and can be used to automate the whole preprocessing. Its just copy paste from the history into a journal file and you already can edit parameters by hand. To rebuild the model you just have to press play.
To add new material properties cubit got a Material Interface. The interface is available in the sdk so i will have to add new properties into the plugin.
Once they are defined for cubit you could already access and change properties via the command line. The gui part still needs to be coded.
Currently the Conductivity, Density, Elastic, Expansion, Plastic, Specific Heat keywords are available via command line and gui. I will add compression_only and mohr coulomb if you need them.
Do you need other keywords or features?