PHP in templates is so last decade
Installing a new template will be as easy as uploading a new folder to your website, going into Extensions / Templates and picking from a drop-down list.
hcg_templates is a modified version of mcw_templates. The _templates folder was moved from the /textpattern directory to the web root directory. This facilitates developing templates now and into the future, with no worries about the Textpattern core files moving or being protected with an .htaccess file, thus breaking your design.