If Balduran was to be ressurrected, it would be as a separate entity from the mind flayer. Withers explains that Mind Flayers don't have souls and that the soul vanishes when a host is transformed. It is uncertain if this means destroyed or moved on to the afterlife. If the latter, a sufficiently powerful Cleric might've been able to ressurect pre-transformation Balduran, but Mind Flayer Balduran can't be cured that way because it has no soul.
