Instead of the majority gearing up on Master Mode Hammer Station (due to quickness), how about adding unique drops in each or several of the Flashpoints so that people do different ones for variety?
Beside the armor,mod and enhancements, there could be special decorations, flairs, pets, mounts, specific cosmetic drops/weaponskins on the different Flashpoints.
Blood Hunt/Mandalorian Raiders could have mandalorian styled gear and decos, Battle of Rishi could have Rishi themed weaponskins/clothing/decorations, Manaan could have underwater/aquatic themed drops, pet, clothing/armor, weaponry etc and so forth.
That way i am sure there will be some more variation and people trying out other Flashpoints as well.
Some extra added incentive.