If you freeze it for 24 hours it will kill them off. Can be a good idea to do that when it comes into the house anyway as they might be in there already.
Easy enough to separate them out of the rice after freezing too.
The limitation with the approach (of HTTP=>HTTPS redirects) is that your average coffee-shop-wifi-user may not notice if their connection does not upgrade to HTTPS due to malicious interception of their connections.
With HSTS, once they've connected to the server over HTTPS once (e.g. at home), every connection from that browser will be immediately upgraded to HTTPS before even trying HTTP.
Your suggestion is valid - as HSTS is only delivered over HTTPS - and the upgrade is still required the first time.
Happy to have a level of group synchronisation out of HR's systems, but certainly would not give them the ability to manage the high-power users.