Could anyone explain the way(s) in which languages which only allow one
finite verb per sentence cope with "if... then..." sentences, e.g.:

"If you had arrived on time [then] you wouldn't have missed the crucial
first ten minutes".

Also, in the book "The Dyirbal Language of North Queensland", kindly
recommended to me by this list (thanks Sylvia), it explains how a verb with
an ergative subject can be followed by an intransitive verb with the same
(now nominative, or absolutive, subject) and vice versa; however, it
doesn't give technical  terminology for the phenomenon. I believe the first
example would be termed antipassive, but what is the term for the second?