I agree Chris, you are absolutely correct. If we choose to widen the terminology of voice to all operations that have the function of changing valence of verbs or otherwise change the focus from one argument to another semantically then these are of course all voice operations. I wouldn't personally use that terminology in neither the case from Inuit nor from Ixil maya.
To be honest, the more I learn the less useful I see voice as a catch all term. I'd much rather see the operations labelled voice in terms of three or more separate functions that they generally perform:
1) removing or making peripheral a core argument
2) marking pragmatic factors like topic or focus
3) altering the syntactic pivot
4) otherwise altering the argument structure of the verb (including adding core arguments)
Most things described as voice perform at least one or two of these functions, but voice operations from language to language don't seem to be a well defined or comparable group, since a superficially similar operation (say passive) can be used in very different ways from language to language. It seems to me very dubious that even a very restricted part of voice like passives can truly be treated as in any sense equal across languages... it seems to me that nothing should be just described as say a passive or an anti-passive or any other kind of voice without a thorough description of what, exactly, it's used for in discourse.
But if we must talk about voice, I maintain that for all intents and purposes many ergative languages have passives.
But both certainly do fall under the wider description. But under the wider description then I do think that the difference illustrated in the example "john paints the paper" vs. "john paint on the paper" is also describable as a voice operation.
Functionally it is equivalent. But I was working under the assumed definition that a voice operation like a passive requires a non-zero marking of some form. As I've said though, the more I think about it the less interesting or useful this whole debate seems, since it's all a matter of minor differences in definition.
Try the online version of the HaSC sound change applier: http://chrisdb.dyndns-at-home.com/HaSC