Nickname problem

Hello there,

Thank you for your awesome plugin. I started to use the plugin today and when configurating it, I found something quite confusing.

The default Display Name in Field Management is a Textbox, while in WordPress user profile setting, Display Name is a Dropdown.
Because of (1), users are able to be allowed to edit their Display Name using any strings, yet WordPress will override that with either the combination of First Name and Last Name, or Username.
And there’s no Nickname in the default Field Management. Unless admins know the WordPress Nickname Meta Key, users are not able to set their own nicknames, and UM (or WP) uses their Username as their nicknames, which is not good.
I suggest:

Display Name should be changed from Textbox to Dropdown, and perform in the same way as the WordPress default one.
Provide Nickname in Field Management.
Allow Nickname to be chosen as Display Name.
Allow Nickname or custom field (which is a textbox, for non-English users to type in English string other than their username) to be used as Profile Permalink Base for security reason. (A job which many WP custom author slug plugin can do well.)

Many thanks.

https://wordpress.org/plugins/ultimate-member/