...and every single piece of code in your entire code base that touches these classes (and that's like 80% of the higher level code in this particular case) wou

...and every single piece of code in your entire code base that touches these classes (and that's like 80% of the higher level code in this particular case) would have to be templated. So either everything has to be in headers, or you need 3 (well, 5 in reality, I abbreviated the example) explicit template instantiation declarations per function in the header and as many explicit template instantiation definitions in the source file. Either way lies madness.