It might be worth coordinating PP-773 and PP-479 as @subhasisb just wrote (in PP-479):
I personally like the idea of treating array subjobs as normal jobs; to that end, I wonder if it would be better to change behavior globally (but allow backward compatibility), e.g.,
qmgr> set server enable_subjob_mail = true
(or “disable_subjob_mail” if we want to default to be “on”).