You can use define ('WP_POST_REVISIONS', 2); in wp-config.php for two revisions, and you could turn that into your own plugin.
Manully remove all revisions with this query run in phpmyadmin:
DELETE a,b,c FROM wp_posts a LEFT JOIN wp_term_relationships b ON
(a.ID = b.object_id) LEFT JOIN wp_postmeta c ON (a.ID = c.post_id)
WHERE a.post_type=”revision”
and then optimize.