Hi Daniel, 

In case you don't hear back from the NVDA team soon, can I ask:  Have you looked at the affiliation of the authors of each of those E-speak NG voices?  I think for the most part that those authors may be unaware of NVDA's existence.  Any phonetic issues are the responsibility of the e-speak maintainers and not, I would  suggest, within  NVDA's purview.

And coming back to RHVoice. Do you prefer robotic voices because they can be played at speed?  HTS voices are playable at high speed intelligibly too. 

- Mark