Thanks a lot!... for testing through HTTP_REFERER and switching to the REQUEST_URI + cookie via checkbox on the Query entry... that sounds like a good solution!
To give you additional context, and as far as I know, people visits the WAP version of the site on a daily basis on their phone, and we'll only be using the ?keyword=value URL string inside the WAP site's iframe, and more specifically, loading a speed-optimized theme for that (e.g. one with no header, sidebar/widgets and footer).
While this is quite an edge case, I hope this will be useful for other users of the plugin (for some sort of "Embed this post" functionality perhaps?)... and will not clutter the settings page too much.