Light is all relative. Light might be nicer to carry, but it comes at a price. Lighter parts tend to be more expensive and for the few ounces that you save, well, it might not be too cost effective.
There are skeletonized stocks available, as well as things like carbon fiber hand guards, but the reality is that the R-25 chassis is heavy because of it's overall size, not the furniture.
I run our PTG-10 in .308 with a fluted, stainless, 16in barrel, and when I slap my suppressor on it, she weighs in at 14lbs loaded.
Seems like a lot, but I find that it settles the rifle into my shoulder on stand, and steadies it while I am taking aim. I find that lighter rifles tend to waiver a bit for me.
If it's a shooter, stick with it and forget about the weight. If you can't, then you gotta let it go.