I think starting system as a discovery exclusive one is a solid idea. And if it won't be Penny, I think Sigma-15 / Luneburg is a good one. Close to Omicrons, Rheinland and rest of the Sigmas. And Hammersee is a desperate, poor place, giving a good athmosphere to start freelancing right away. Also it is a good place to introduce Rheinland politics, and the Core.