Yep, the Nintendo 3DS came with a 1750 mAh battery and that lasted for 3-5 hours. Get a small power bank or a 10,000 mAh one and you're set for the whole day. I don't think battery is too much of a problem.
Yup, agreed. I have a big powerbank i use for everything at home and i see no reason to increase the bulk of the Switch itself to include a bigger battery.
Likewise if it wasn't built in but came with the product, i'd be wanting a lower priced product not including the external battery.