Gross, no thank you.

18650 would be cool though.

I'm with you. I loved how the AAs slotted into the handles of the original steam controller. I bought some Eneloop rechargeable AAs for it that still work great. I use them in my toothbrush, which I also bought because the rechargable lithium version died. The AA battery version of the toothbrush was like 1/5 the price and will probably last forever

You can remove the 9 screws in the back of the controller and fully remove and replace the battery. Going by valves track record they will have replacement parts on ifixit. Also one of the engineers confirmed while speaking with tested that you can easily access the battery compartment and interior of the device and replace it.

Why not all 3 options, sell a controller with a removable, rechargable battery pack & able to play with a cable in while charging, and if you remove it it leaves room for batteries instead.

One of the nice things with Xbox 360 controllers were the rechargeable battery packs. By default, the controllers used 2 AAs, but you could instead use a battery pack. Just remove the AA battery cover, pop in the rechargeable battery, and that's it. You could then connect a cable to the controller to recharge the battery. And, if the battery happened to be empty (or dead because of old age), you could just replace it with 2 AAs, and continue playing. Some of 8bitdo's controllers uses (or used) the same design, but they come with a rechargeable battery pack in the box.