If I were the FCC, I would issue "transmission licenses" valid for 10 years, to anyone who wants one for the unlicensed bands. The license would be a signed digital file shipped on hardware. They would work like let's encrypt - when nearing expiry, your device could auto-renew its license via the internet. It could transmit its license via a wifi beacon packet, allowing other devices to use the license too (with the same expiry time).
Basically, if your device is offline for 10 years, and isn't in range of any other online device for 10 years, then it will stop working.
The license would list frequency bands and power levels. That allows the FCC to decide to limit power later, or reduce/widen frequency ranges, and devices already in the field will start to comply within 10 years.
A few bands intended for less smart devices (ie. doesn't have both transmit and receive, isn't digital, doesn't have a clock or storage, etc) wouldn't require such licenses.