How about this for an end-game credit sink:
CMDRs are called on to donate credits to Lakon, in order to guarantee their future independence. Donations can be lodged at <wherever>; donations will be closed when the total reaches <insane total>, or after one week, whichever comes first.
Should this donation drive reach certain defined tiers, contributors will receive the specified tier reward, including at top tier a new, exclusive Alliance vessel that may or may not resemble the Panther Clipper. This ship will not be available for purchase through normal channels.
(No, I don't expect this to actually happen. And neither should you.)