In 2014.1 the "server.depot.root" configurable was added to specify the location of versioned files. In some cases, it would be useful to be able to set this by a p4d command line option as well.
Earlier this week, I was recovering a p4 replica server from a checkpoint. I decided to separate the databases from the versioned files onto two separate filesystems at the time. While could set the server.depot.root configurable on our master, that new setting wouldn't be in the checkpoint I was restoring.
I ended up rotating a new journal after I set the configurable and applying the additional journal to the replica, but setting the depot root from the command line would have been easier. In fact, if this proposed command line option was available, I'd remove the server.depot.root configurable setting for all our replicas.