Auto registration of new custom columns from plugin code [question/feature request]]

Is it posiible to write a Calibre plugin that would automatically ask Calibre to create some new custom columns?

For example: i have some download metadata plugin "A". This plugin has a configuration option: Fetch number of ratings: true/false. If user enables this option i would like plugin "A" to automatically ask Calibre to create/register new custom column "number_of_ratings" if it does not exist already