Pagination, query more pages at once

offset would skip posts, it sounds like you want the current page number * the number of posts per page-

$paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
$posts_per_page = $paged * get_option('posts_per_page');
$args = array( 'posts_per_page' => $posts_per_page );

You’ll need to keep in mind that total number of pages in the query object will change as you change the number of posts per page, so you’ll need to keep track of that yourself.