Preventing indexation of sites without a mapped domain (i.e. dev sites)

Since most sites without a mapped domain are in development, is there a way to prevent the indexation of sites without a mapped domain? If not, are there any plans to add an option in the network settings to link the search engine visibility (Settings > Reading) to the domain?

So for example, when this option is enabled any site without a mapped domain will discourage search engines and any site with a mapped domain will allow search engines. If this option is disable, then it works as it does now, leaving them independent for people who want to use sites like blog.domain.com.

Sure this can be done manually, but it’s tedious on large networks and the chances of leaving search engines discourage are a significant risk.

https://wordpress.org/plugins/wordpress-mu-domain-mapping/