Thanks for the answers. I asked someone on ghallanda these questions as well. Seems I didn't look correctly at first but with this new pc ( and big screen ) I saw that the GS clickies are all Displacement goggles. Dunno if quarterstaff is better to slot those as in the OP but will come to that later. Also, my questions about mithril body are also clarified. You can drop it to go bludgeoning weapons (sireth et all) and grab other twists. Wasn't very clear in the OP as well but that's why I thought I should reply.
Seems any Past life feat is fine for the Ranger version. But I think Ranger and Monk are the best choices for this for added damage to both ranged and melee damage.