The Wellington and the Halifax both preceeded the Lancaster. These three planes (Lancaster, Wellington a.k.a. "Wimpey", and Halifax) made up the mainstay of Bomber Command throughout the entire war. Especially the early war. As it is we really only have the Lancaster for brit level bombers, and it's mid-war at best. We need the Wellington and the Halifax to better represent the early planeset. While they could still carry good loads (I think the Halifax also carried 14x 1k bombs) they were lightly defended and slower, and had much less powerful engines.
I say we need both! Halifax AND Wellington!!!
The Wellington was supposed to be VERY sturdy, due to its latice-work wooden frame. Suppose that means it could take a lot of damage, but once it caught fire I guess it'd be like B24s (evil grin here).