On principle I believe batteries should be replaceable, regardless of their chemistry. Throwing away an otherwise working device because it was made with a non-replaceable rechargeable battery is wasteful. That said, the lithium chemistry rechargeable batteries have been improving over time and product designers have been making lighter and brighter lithium chemistry powered lighting products, My main ride has a dynohub and powered lighting front and rear so no real batteries there other than my wrist worn Garmin Foretrex 601, which I use mostly with rechargeable AAA batteries or disposable (and increasingly expensive) Energizer lithium AAA batteries. On other bikes, we use a collection of Planet Bike Superflash Turbo and Portland Design Works rear blinking lights with the aforementioned rechargeable and disposable batteries. We do have some rechargeable lights around but they don't see much use.

I would like to see a device that could use multiple types of batteries and be able to charge NiMH or LIthium rechargeables by connecting a USB-C power cable. Unfortunately, while technnically possible, without proprietary cell packaging so the device would be able to detect what type of battery chemistry was installed, such a device would rely on the user to make sure they didn't try to charge nonrechargeable cells or use the wrong setting for a particular cell chemistry, which in turn might increase the risk of fire or explosion. That's why it is uncommon to see devices that can use either replaceable disposable or rechargeable batteries have any ability to charge batteries in the device.