apriorit

This plugin allows you to more conveniently manage the creation of multiple sites within a multisite. 
Now you can create subsites and their pages with just one click.

Site Generator

This plugin allows managing creating multiple sites within a multisite more conveniently.

Daniel Westermann-Clark

By default, WordPress network usernames cannot contain anything but lowercase letters and numbers. This plugin adds network options to let you include hyphens, underscores, or uppercase letters, if desired.
Furthermore, this plugin gives you the option to allow email addresses as usernames, or to allow all-numeric usernames (e.g. “1234”).
Finally, this plugin lets you override the minimum length for usernames (which defaults to four characters).
To follow updates to this plugin, visit:
https://danieltwc.com/
For help with this version, visit:
https://danieltwc.com/2011/network-username-restrictions-override-1-0/

Network Username Restrictions Override

Does what it says!

Override restrictions on WordPress network usernames.

Site Generator vs Network Username Restrictions Override