allow user on registration to choice group

can you add a function that will allow user to select which group(defined by admin in backend settings) wish to belong while registering with provider (login in for first time and creating account) for example
1) Free Customer
2) Paid Customer
3) Beta Tester

as popup after account is created based on
www.function90.com/docs/usergroup-selector.html

Slogin sets the group of settings specified in Joomla.
If you need a specific function we can develop an extension on a commercial basis.