Strange construction pops out of nowhere

Folks, I need help checking whether this is
a good idea or not, and in any case what do I
call it. This construction appeared spontaneously
while I was working on my grammar.

SYV has several enclitic copulas: one is the plain
"essive" copula |de|, and then there's the "transformative"
copula |mo| (I need a better name for it too) and the
"causative" one |komo|.

Yue leade. "Night is black."
Yue wo leamo. "This night is becoming black."
Ekheba leakomo yiyuech. "Clouds are turning the night black."

The causative copula |komo| is intended to mean
"cause to become X". I thought it would work with
the same structure as |de| and |mo|, which just
attach after the predicate, but of course |komo|
needs another argument. I figured all three arguments
should be case-unmarked, since core cases (and
predicates) always are. I played with word orders
and everything seemed too ambiguous, or unwieldy
for more complicated noun phrases.* So I just
stuck the genitive mark |yi-| on the patient.
Now, is this natural? How would you classify
such a construction? How do you handle such
predicates in your conlangs?

(*) |lea| "black" is just one syllable here,
but one can use a noun predicate with |komo|,
maybe even a long, complex noun phrase.

--Pablo Flores
  http://www.angelfire.com/ego/pdf/ng/index.html