The Jumo type designators "214" to "221" just seemed to be space holders
for probable further developements of the Jumo 204 to Jumo 211,
which have not been used for concrete developements.
Just the Jumo 218 is known as a further developement of the Jumo 208.
The Jumo 218 was a coupled engine of two Jumo 208.
This idea was born for the demand of several high altitude designs
such as the Ju86P or the He177B.
However, the Jumo 218 studies were stopped at an very early stage.