... if you want a mass storage device... buy a mass storage device?
Personally I'm happier with the cloud though. I want all my files in the cloud anyway as an offsite backup, and the internet is generally fast enough that I can access the remote copy whenever I need it.
> Be switched on immediately when plugged in, after the battery runs out
My battery never runs out though.
But seriously iPhone CPUs are pretty power hungry with 3.46Ghz with six cores and aside from just booting up there's also some pretty high decryption going on to decrypt and verify the operating system hasn't been tampered with. I'm pretty sure a USB cable can't provide enough watts.
> Want to use a keyboard/mouse/monitor to control your phone instead of your thumbs
USB and Bluetooth keyboards totally work with iPhones, and iPads. I use a mouse and keyboard all day long every day with my iPad (I'm happy with my thumbs for my phone, but I could use the keyboard for that too).
And you can absolutely connect it to an external screen too, with HDMI or over a network connection.