Again the Camera kit allows you to do what you want swap via SD cards on and off and also USB and cable with one exception and that's the thumb-drive.
Apple does not allow data transfer that way because iOS doesn't have an accessible file manager.
You really need to buy the camera kit.
There are also practical reasons that USB and SD card readers are NOT on board they take space they make the device thicker and heavier and they need their own controllers and power adding further space and weight.
The Lightning/30 pin sockets significantly reduce the weight and energy consumption that USB and an SD cardreader would involve
Again install bump its third party ad-hoc Wifi for file transfer with almost any device including your Android friends or your PC no 3G or Wiifi necessary.
You need to do some configuration and software tests.
I recommend bump, Goodreader and Dropbox in any tablet setup.
All that said I think you may have made your mind up that for you legacy support may have value - Suggest you try a Surface if you can stand that W8 look and feel and limited software options oh and dire battery life.