I think that the arity of predicates should not be an up-front constraint on
how to build an ontology.
I also think that the tension between the objective of formalization and the
objective of coverage will continue for a long time, and people will continue
to make choices based on external requirements (e.g., project specifications)
or, in the absence of such, on whatever they feel more comfortable about (this
explains the opinion in the previous paragraph).
Cheers
Sergei