I would argue that if you add 3G/4G and tethering it's no longer a feature phone. The Nokia 215 isn't really a feature phone either, it's a low-end smart phone.
A feature phone that doubles as a 3G hotspot seems like a weird idea. You would add semi-expensive 3G chip, but not use it for the phone is self.
Fair point. What I meant was a phone that does calls and texts the majority of the time (no need for 3G) but has the ability to connect to a 3G (or better) network if needed and can share that connection via some wireless means (wifi, bluetooth).
Perhaps I just mean a mifi device.
I kind of like the option of having a multi-day battery life too.
A feature phone that doubles as a 3G hotspot seems like a weird idea. You would add semi-expensive 3G chip, but not use it for the phone is self.