Viewport meta added twice for some themes

I have noticed the viewport meta tag is included by default with this module. Now I understand it is documented in the module about maybe removing this and have themes manage the viewport tag, and that many in fact do not.

Unfortunately some themes are hard-coding the viewport tag right in the html.tpl.php template, such as Zen. This makes it impossible to check for the viewport tag in preprocess and process functions, or even the template_html_head_alter() function. Otherwise we could simply search for it and choose whether to include it with Adminimal Administration Menu.

Perhaps the best option would be including a module setting to add the viewport tag? A decision to be made, tell me if you agree/disagree on this, would be whether to include the viewport tag by default. The administration menu does become rather unusable on smaller devices without it, so being added by default seems sensible to me. Then those who want to disable it can easily do so on the current module's configuration page.

I set this to a support request since the module already includes the viewport tag, but also because I want to open it up to discussion before it is considered as a feature request.