Yes, that’s an excellent idea. Maybe different flashing sequences for the phases of the update too in case it gets stuck for some reason (such as with my case where I had a non-standard DNS forwarding setup and the kresd behaviour changed).
I previously installed the Turris app on my phone so that could be another way to display a message about an update in progress, though obviously the message would have to be pushed before the network was modified. (I didn’t see any messages this time due to multiple reboots, but unfortunately for the last Turris OS update the messages were shown in Czech despite both the phone and Omnia being set to use the English locale).