Hi joiecito,
My guess is there's some sort of engine incompatibility in the Maya plugin, I was able to reproduce at least the opacity map issue. For me, it renders completely white. The normal map looks like it's losing some details as well.
We won't be doing any more updates to the current plugin, but there's a new plugin that should be out soon. I tested it on that, and it looks like it renders correctly, so I think the issue should be fixed when we release the 2.0 plugin in the next few weeks.
Best,
Galen