I am not sure how two synced HA instances (if that’s even possible) would help. You would need to allow your IoT devices to be accessible by the Home Assistant instance you want to use with your personal devices. If that seems like a risk to you, then why not run HA in the DMZ alltogether?
Dashboards can get quite complicated and funnily enough TV remotes are not all the same. With a small userbase (it is by far not the most requested feature) it will be hard to maintain such a feature without just fulfilling a one-user-usecase.