While we're talking about new features

[Shawn Wagner]

Two more I have in mind:

Supporting a GNU sed extension of taking both a starting offset and g
with s///Ng - replace all matches starting with the Nth one. I have
this mostly done; I'm not sure how it should interact with the current
toggling behavior of sN and sg, though.

Adding an ex-like range to ! that sends the addressed lines to an
external command and replaces them with its output. I don't think
there's any good way to do this now that doesn't involve multiple
steps and a temporary file.