In the game I'm about to kick off, one of the players are kicking around an idea of playing an Emissary of Cerberus/Garm, essentially a local "deputy" that Cerberus sends after people mucking around with the dead (mostly necromancers) and occasionally regular ghosts.
In order to physically interact with ghosts in the mortal world, OW p56 says three things are required: Some form of magic, knowing the ghosts name, and speaking that name out loud.
Would it be cheapening things too much to allow the power Ghost Speaker to also allow physical interaction with ghosts, thus bypassing the necessity of knowing its name? Of course, they would be able to affect the user physically as well, with no need to further materialize.