Items 3 and 4 seem like weak arguments. We are still dealing with operating systems from 3+ years ago, so moving below a 1 year certificate length wouldn't buy much agility in terms of new algorithms.
A better example would be something like Certificate Transparency. Currently, browsers may require Certificate Transparency for certificates issued after a certain date. A malicious or compromised CA may work around this by backdating certificates. This would be less of an issue with shorter certificate lifetimes.