From an ATC point of view - doesn't matter what you call - ANY loss of 50% of available power plants is an automatic "full emergency" - regardless of the r/t call you made.
Also, in my 20 yrs, not only have I NEVER downgraded an emergency, once declared but as I understand it, the RFFS will refuse to downgrade anything, once they're aware of it. It is preferred to make too much effort and not be needed than not enough and be damned!