With the GrabResolver in Groovy/Jenkins (http://docs.groovy-lang.org/2.4.10/html/api/groovy/lang/GrabResolver.html), you can add additional repositories to the resolution chain. I would like to remove all standard repositories (as MavenCentral), but I did not find a way.
The reason: Those repositories are not available inside our company, and contacting them until timeout wastes a huge amount of time in the process.