When I get this right, I will be pulling my hacked code out of features.php which checks the URL/pagename of the current page that's loaded to determine if it's the home page or any other. I had an "if-else" in features.php. Inappropriate location for logic, but it does work

I haven't successfully implemented your technique yet, this non-functional example doesn't use an if statement, instead placing a hardcoded home page layout inside the else which determined the CONTENT_INDEX_DEFAULT.
Original code from index.php:
} else { // default page
$content = CONTENT_INDEX_DEFAULT;
}Changed to:
} else { // default page
$content = CONTENT_INDEX_DEFAULT;
// t added to hardcode alternate home page layout which can have it's own stylsheet, layout but will also need hardcode box inclusions
define('TEMPLATENAME_MAIN_PAGE', 'myhome_page.tpl.php');
}This failing to work, I then tried placing the define('TEMPLATENAME_MAIN_PAGE', 'myhome_page.tpl.php') inside an if statement you suggested, at the bottom of the file, but haven't got it right yet.