Almost three years ago now I added my thoughts on this issue.
I've changed companies twice since then. Provided-dependency support is an issue in each place, whether the issue is a in some form of "container" or wrapping library (Tomcat, Jetty, Hadoop/Spark, etc) or simply writing to a spec (servlet-api). In each place someone has had to either add a third-party plugin to support provided/providedCompile, or write it afresh. Each implementation is just enough inconsistent with the others that the result is... in polite company, deplorable.
Is there at least any insight to share on what difficulties lie in implementing a provided / providedCompile scope, in the Gradle 2.x world? At worst from my vantage point, the WAR plugin needs to play nicely in the case where some other plugin has already added provided / providedCompile.