Hello, Martijn,

> Any idea if this would be possible, easily? Are DEFERRED constraints
> used a lot? ( I can image this for database wide constraints instead of
> table wide)

I use them often in Oracle. One important use for them is replication.
It is easier to apply replication delta that moves database
from one consistent state to another when using deferred constraints.
No need to maintain integrity during this process it it is performed
in one transaction. Adding them to FB is not difficult, really.

Nickolay Samofatov