How about an extension to the task path syntax to handle this instead of more command line options.
Something like appending a '!' character to a project or task name to mean - just do this one without dependencies.
For example - in a two project system (consumer, provider subprojects), consumer depends on provider:
This will run full lifecycle (init-libs) on provider before init-test of consumer
This would only run init-test tasks on consumer project (ignoring all task dependencies on other projects)
This would run only the test task only on the consumer project (ignoring all task dependencies) .
This would run only the test task in all projects.
In a large build system this can be very handy when you are trying to repeatedly run a task in a single module and know that the archives for the dependencies have already been built.