Regarding tuning keys - the Tribute ones are quite heavy, definitely heavier than Schaller BM. You can buy the USA tuners direct from G&L when they have stock:
Tuning Key - G&L USA Ultralite Bass - G&L Online Store
They might not be a straight swap, might have to drill new holes.
Then there is the Hipshot Ultralite if you really want to shave a lot of weight off the headstock. The 1/2"-post model will fit with a bit of extra play in the post hole; not a problem once they are tightened.
I appreciate your info, but as for me, I'm not going to add $200 (+shipping) to the price of my Tribby to reduce the headstock weight. Then again, I don't have an issue with it.
) Congrats!