Few years ago I would have jumped in the bandwagon and stretching my energy to the max just to test this. But nowadays I need a reliable musical instrument which will perform as I desire with an easy to use UI. Same as MONTAGE8, the voice synthesizer must be easy to handle and to edit in real time.
I think Vocaloid5 editor is en route to have neural-networks implemented soon, therefore I won't need "just another engine". (Expecting Piapro Studio to become neural-networks too)