Frankly, I do not have any plans to modify the plugin as my understanding is it isn’t needed.
The action of consent is given by the action of entering the name and e-mail address into a form specifically for the purpose of a mailing list. Any required text can already be added in the widget text. A checkbox to say “yes, I’m giving you my e-mail address and name” when all the form is doing is asking for your e-mail address and name for a subscription isn’t in line with my understanding of the GDPR.
A checkbox opt-in is required on, say, an account registration form or some other time you’re collecting personal information where it isn’t clear that you’re going to that information for the purpose of e-mail marketing.
If your compliance office would like to have a checkbox, you can add within the “Hidden Fields” box a <input type="checkbox" id="subscribecheckbox" name="subscribe" value="newsletter" required="required"><label for="subscribecheckbox">Subscribe to newsletter?</label>
For the styling aspects, that is theme territory. The plugin is intentionally shipped without any styling so the folks at StudioPress or other theme shops can fully customize the experience without having to clash with default styling.
Having an easy to use way to link to the privacy policy makes sense to me and with WordPress adding native support for a set privacy page, I’ll look at making it easy to link to that page. ( https://github.com/kraftbj/genesis-enews-extended/issues/140 )