All you need in an alternate reality maybe, but in this world, line numbers on Source View are pretty essential to anyone who has ever made a webpage.Composer
SeaMonkey's powerful yet simple HTML editor keeps getting better with dynamic image and table resizing, quick insert and delete of table cells, improved CSS support, and support for positioned layers. For all your documents and website projects, Composer is all you need.
*sigh* not holding my breath on this - the bug for it is only TWENTY ONE YEARS OLD! - https://bugzilla.mozilla.org/show_bug.cgi?id=99211
Edit - is Find on Source View bust as well?