I have searched the web all over this question and I have not really found an answer to my satisfaction. From my understanding of the topic so far, I understand that reason why concept of unified atomic mass works better than providing absolute mass of protons/neutrons (in grams or kilograms) is because "u" provides between clearer presentation of relative masses among elements in whole numbers than the negative exponents would in regards to absolute mass. If this premise is true than why not define atomic mass unit in terms of multiple of protons and neutron? Like since proton and neutron are roughly equal in mass ~ 1.66* 10^-24g. Why not say 1u = mass of one proton and 1 neutron. Why does the definition of amu need to include 1/12 of carbon 12, because mass of 1/12 of carbon gives me mass of 1 proton 1 neutrons and this seems redundant to me?
But now if we accept the definition of amu as 1/12 of carbon 12? Why not include other elements like amu is 1/1 of Hydrogen atom, 1/4 of helium atom, 1/16 of oxygen atom, because all this would would give me same value of 1u= 1.66*10^-24g ? If anyone can give their input on this, that would be grea.