Using with and without base- templates for the same pages?

Hi, I started using Sage after I saw that it supports the Gulp-kind of builder-methodology and am pretty much happy with it. I’d like to have a conditional based on the querystring which shows the total clean version OR the wordpress-themed version of the page. But this needs to be done on the base-xxx.php files. Thus I need to switch the ability of theme-usage by a queryvar. Is this possible and how? Thanks.

See “Filtering the wrapper: custom post types” for example usage at

or if you want to skip the theme layer.