I find it much more convenient to press a button that’s already under my thumb and then press a button that’s already under my middle finger (for example) to get a symbol I want than move my hands from their typing position to get a symbol. It takes some time to adjust but I’m at about the same speed I was on a standard keyboard while using a corne (like the lily58 but with no numrow and one fewer thumb buttons per side)

Also space is right under your thumb as well, and shift can be in its normal place

Take a look at stuff from keeb.io, most of their split offerings can run with either side as the ‘host’ as far as I know

I think you might like the design of the typeractive.xyz corne where the put the battery under the MCU and have headers to give space for it

I put my arrows on a layer under hjkl but I’ve also heard ijkl and wasd are popular for that

Check out the quefrency 65 rev 5 by keeb.io. It seems to match your criteria pretty well. For palm/wrist rests I use two purple squishies

When they say dying battery, I don’t think they mean discharging. They mean the battery has reached or is reaching the end of its life in terms of charge cycles and capacity