Among the many changes, the new rules would require batteries in consumer devices like smartphones to be easily removable and replaceable. That's far from the case today...
Seems like you could just mandate manufacturers to make sure replacement batteries are available on the market as well?
I'm a few years into my Fairphone 3, it still lasts two days of normal use without charging, and the battery can be replaced in seconds. If I need a new one I can buy it straight from the producer.