I think the big issue is that not every email client reacts harshly enough to emails with either no DKIM header or mismatching DKIM signature. Today it's basica

I think the big issue is that not every email client reacts harshly enough to emails with either no DKIM header or mismatching DKIM signature. Today it's basically just one of several factors for marking a email as spam, when in reality it should show a big-ass red warning.