... The
problem only apparently comes up when there is no prefix (but I can pronounce
[kpar] too). ...
In many African languages words start with "kp". In fact this is usually
a "double articulation", the air stream being closed with both the
tongue and the lips and then released from both simultaneously. Try it.
I doubt if this was ever the Hebrew pronunciation, but at least this
proves that such a pronunciation is not impossible.