> What if some people should have more or less say in something.

Yes, I certainly agree.

The problem (which IMHO outweighs all the benefits by quite a bit) is that when you allow drawing these artificial lines the ones in charge of them will inevitably design the system in such a way that benefits them (maybe even without ill intentions).

It's similar to geographical gerrymandering just openly based on social/education/etc. class.

Also... balancing interests of diverse social and economic groups is not exactly straightforward, its certainly not basic math.