Small example on how to manage multisite with some global user fields and some site specific fields.
It only contains "sites" folder of drupal, where in "all" folder is the common configuration and in site-specific folders ("d7-features-poc-en" and "d7-features-poc-nl") are the site specific features.
In our case, “user_global” is a feature with common fields, “NL” site has one NL-specific field and “EN” site has two EN-specific fields.