More granular control IPv6 address assignment

As a system administrator, I would like the ability to specify an address from within a range when enabling IPv6 for an account, as this provides me with more granular control of IPv6 address assignment.

-------------------------------------------------------------------

At current the only method to assign a specifc IPv6 address from within a range is to trick the server into thinking that IP was already used once, and then toggling an account until it receives an address.

I would like to see the ability to specify an address from within a range when enabling IPv6 for an account. I've attached a mockup of what it could look like.

Defaults to Auto Assign, so the current behavior wouldn't change, but allows the option of specification.