The question now has changed much more from "How light -can- it be" to "How light -do I want- it to be". Pretty good "problem" to have!
Agreed.
Although, I can say that at least with the 223/5.56 cartridges, and with a suppressor installed... even the lightest configuration possible (8 inch barrel with a red dot) isn't unpleasant to shoot, and the weight isn't so low as to make the recoil mess with my shooting.
That said, I think my real interest comes from shaving ounces from the rifle so that I have the option to add them back in with higher performance add-ons.
For example... I love my Scythe Ti suppressor. At 8oz, it's about the best suppression I can get. However, when I put my Resilient Jolene suppressor on the same rifle (which adds 2.7oz) it is almost night and day in the level of suppression performance. So, if all else being equal, I can shave 2.7oz from the base rifle platform... then I can justify the use of the quieter Jolene, but be at the same overall weight that I had started at.
Likewise, my SWFA ultralight 2.5-10x32 is a great and very useful scope with the bdc reticle. However, for a 9.87 ounce weight penalty (by comparison) my Nightforce NXS 2.5-10x32 is a vastly superior scope. So, if I shaved those ounces off of the base rifle... then I get to enjoy the same overall weight (but with much better scope) than if I had just left 'well enough alone' at a 3lb base weight rifle... and in truth, that's exactly where I'm at now. My first straight pull build last year was right at 3lbs bare rifle. Now I'm at 2lbs 4oz. That 12oz difference let's me have the same overall finished weight now with a Jolene and the NXS as I did last year with the Sythe and the SWFA... same final weight overall... but better performance with the current setup because the weight savings let me upgrade the accessories.