I think this was somewhat intentionally designed to only take a single required argument. Checkout the existing docs for the history server:
http://spark.apache.org/docs/latest/monitoring.html

Doesn't this also break compatibility with 1.0 as well?

Separately, I'd rather not overload `-D` in general. This seems to actually have different syntax than the normal `-D` where you do `-Dkey=value`. Here it's `-D key value`.