In the latest implementation of the openshift-java-client I added classes that shall allow users to drop hard-coded cartridges:

IEmbeddedCartridgeConstraint
ICartridgeConstraint
IApplication#addEmbeddableCartridge(IEmbeddableCartridgeConstraint)
IApplication#removeEmbeddableCartridge(IEmbeddableCartridgeConstraint)
IDomain#hasApplicationByCartridgeConstraint(ICartridgeConstraint)

I did some tests for the IEmbeddableCartridgeConstraint, but none for the ICartridgeConstraint yet.