While it was a B.Mk IX that did the most sorties of any Allied bomber, I think the B.Mk XVI covers for it well enough, just remove the 'cookie' option for settings where the B.Mk IX is appropriate.
While I'd like to see the FB.Mk XVIII added, there were only 27 of them, about half converted from FB.Mk VIs and about half new builds. That is hard to justify on that low of production.
I would very much like to see the F.Mk II, B.Mk IV and F.Mk 30 though.