> company All-Hands should be run weekly, till the company gets to several (~five) hundred people

Sweet baby Jesus and the orphans, no.

I may be biased, because I've never worked for a company that did a true all-hands meeting. My largest employer (~32k FTEs) did a department wide IS meeting (~800) quarterly but it largely just a review of what had happened on the business side in the last three months.

I can't think of a single legitimate reason for a company of ~400 to meet every single week. That's ten man weeks of time lost, every single week, so an SVP half the employees don't know can let everybody know Susie in Finance has been here for a year on Thursday?