The big advantage could be finally moving the PSU out of the case, and having it as just an external power brick. This will make systems significantly lighter and smaller (and thus more portable), take heat out of the case, and improve airflow.

You can already buy 330w laptop chargers - just beef them up and you could easily run a mid-grade gaming PC.

https://www.amazon.com/Dell-Adapter-DA330PM111-ADP-330AB-332... You can already buy