I don't have a fully formed answer for you.
One client of mine is requiring staff to carry a WiFi device on them at all times. This is typically a mobile phone. For some staff, they have bought a cheap mobile phone just to attach to the WiFi (has no SIM card, can't make calls, use TXTs, access mobile, data - just for WiFi tracking).
Several mobile devices use mac anonymization, so you might have to turn this off - or give those staff the cheap phone as well.
They are keeping a register of all staff and their mobile MAC address.
I have other clients you have worked with Splash Access as they have also developed some kind of contact tracing system. They don't seem to have much on their web site about it, so you might need to contact them if you think this is something you might be interested in.