If I understood correctly all msgs I read (sorry but I'm not mother-tongue
and what's more far from having a good English) I cannot alter the status of
the whole package.
Only way is to play with Global Variables. Am I wrong?

Scenario:
Package A
task A1 (execute package task: Z)
task A2 (whatever)

Z, before to end, sets the status to failure
A2 workflow can works "correctly"

AFA I can see the package status is always "success" (but when the flag
"fail on first error" is on which is a bit too rough)

All the best
pf