We have the need to let users choose users from a people picker dropdown....

You do not want users manually typing in what they think a users login name is.... if they can choose the users email address from an auto complete field like CCemail, we can use that to get the username. But that functionality doesnt currently exist. 

$a = ' jdoe@contoso.com'

$a.split('@')

jdoe

contoso.com

$a.split('@')[0]

jdoe

disable-ADaccount -identity $a.split('@')[0] 

Basically we need a way, existing or not, to retrieve a username.....I dont see a people picker in the custom fields section. I do see the JS code for it, but i dont really wanna go there and create a production solution based on it... The only alternative is to let the manager manually type in what they think their user's login name is... that wont work.