added a comment - - edited
I hope this issue should not remain a minor priority RFE.
I think here the focus doesn't lie as much in having any way to produce a war (we can still obtain it in several ways thanks to gradle flexibility) but rather in composing war artifacts based on dependencies between wars, with proper management for provided deps transitivity.
In other words a war project by convention could get transient deps and web contents from other war projects/artifacts it depends upon.
It would be great also having a way to obtain war overlay for gradle projects that enforces complete IDE integration i.e. a declarative approach that lets the tooling api expose enough info about merged resources in order to support the ide on reflecting the overlay as needed (we use eclipse/STS).
I've opened a dedicated thread on the user mailing list.