Go tubeless with something like hans dampfs.
Swapping the fork for something lighter would result in significant weight savings, but also would result in significant downhill performance degradation, so I probably wouldnt do that.
1x 10 would be worthwhile if you're fit enough/your hills are not that long/steep. I'm not fit enough for this though.
To be honest I wouldnt obsess over it too much, it gets expensive and if you're the sort of person that buys an enduro , you wont really appreciate the benefits being lighter brings , but you'll notice the compromises it brings. I speak as a 2005 enduro owner, and a 2010 Ibis Mojo HD owner.
I've just put a Marz 55 rc3 ti coil fork on the mojo, awesome fork, who cares its a pound heavier than a fox 36 float. Everything else on the Mojo is a careful balance between being light'ish weight, but not compromising downhill performance significantly.
I found 'cheap' ways of saving weight without sacrificing downhill performance are :-
- Tubeless tyres
- light weight pedals
- Carbon handlebars
- lightweight saddle
- decent cassette
Anything else either costs an absolute fortune (and some of the above are not really cheap), or impacts downhill performance