A whitelist textarea where you can see crystal clear what IP's are whitelisted, with the possibility to enter comments, would be greatly apprciated, and it's not as hard to code, because it's simply expanding the actual input field and separating the data by new lines rather than commas. The format may be like this:
184.108.40.206 # my home computer
220.127.116.11 # my job computer
18.104.22.168 # Sucuri Scan IP allowed
Since its a textarea, you won't need to code an UI and keep this feature in the free version to benefit your users :)
Also, adding a link to whitelist one given blocked IP may be helpful in the scenario where one may want an external security service to access WP.