It would be nice to have something like transitive dues/deadlines.
Example: an action D is a dependency for an action A and action A has a deadline. If action D doesn't have any deadline set, then assign it A's deadline and if it has, show warning/block when A's deadline is earlier than D's deadline.
Transitive deadlines should be somehow distinguished in GUI (and logically) in order to see they weren't set manually but calculated instead (and allow update when A's deadline changes).