Sort of like "building" a tooth pick out of a Louisville slugger ? Why not buy a toothpick?
Not sure I understand this question ... sure don't understand the sarcasm in it.
Most 21s are substantial guns. My 16 ga. is 6-3/4 lbs., maybe 2 oz. lighter than it came from the factory with BTFE. This weight perfectly fits the Brit's rule of 96 for the 1-1/8 oz. loads I mostly use for wild pheasants. It's also quite tolerable with the 1-1/4 oz. pigeon load equivalents I sometimes use in the left barrel in late season. And I can carry it easily all day.
I can shoot light game loads for doves or at targets without punishing recoil.
Should I be wishing for a lighter gun? Don't think I want one of them toothpicks. Courses for horses as they say.