Multisite install and user selection menu

We’ve installed this plugin on a Multisite install that has ~15K user accounts, so when you go to select a user from the pulldown list the menu is overwhelming.

It would be great if only the users with capabilities on the particular site in question where listed. The other users are just in the way and expose information about the existence of other accounts.

I would suggest something like this in the rul_returnusernames function:

select U.user_login from wp_users U, wp_usermeta UM where UM.user_id=U.id and UM.meta_key='wp_BLOG_ID_capabilities';

https://wordpress.org/plugins/peters-login-redirect/