Yes, that's asking too much. As mud only gets your typed text
_after_ you press enter, mudside editing of your edit line is
not possible. However, this can be done with triggers in TF,
probably (?) doable in zmud/cmud, and possibly an idea for
BatClient (or does it already have it?).

From mudside we have !<num> and !<asd> to access lines from
history, help parser under HISTORY for more information. This
should be enough for most cases, and help command/alias for
the rest.

-Era of idling