I have to agree with Lodder's comment... This is not making a real sense and it probably will create confusion.
But for the sake of answering to your question and to help you find a way to achieve something like this, you could try the approach below:
jimport( 'joomla.application.module.helper' );
$modules = JModuleHelper::getModules( 'yourposition' );
$attribs = array('style' => 'xhtml');
echo JModuleHelper::renderModule($modules, $attribs);
getModules($position) function will load an array with all the modules in your position, ordered by module id.
Then, with the
renderModule($module,$attributes) function, you output the module. But since you have an array, you need to tell which module you will render, by specifying the index of the array's element.
But because there will still be a dynamic way of creating/editing/changing modules settings, I am not that sure how you could ensure what module will be rendered at the end, in the case that other users will be managing the website.
So, if you would explain a little bit more what are you trying to achieve and why, we could propose you the right solution.