Hello,
I'm having my iPad Mini still on 6.1.2 because I wanted to stay at jailbroken state. Without jb it is useless for me, I need iP Firewall, XBMC, ssh access and some more Cydia apps ... I am still buying apps from AppStore.
For now some new Apps from AppStore needs iOS 7.0 and higher so... with a big pain in my butt I'm thinking about upgrading it.

There are 2 questions for you:
1) Is it possible to make a fresh upgrade to something jailbreakable? By fresh I mean to restore my device to factory state, lose all settings, files (dependencies - there I have a huge mess at the system).

2)What I am losing by upgrading to iOS 7? The battery drain is really so painful? I am reading a lot of books on a travel, 6 hours of battery life isn't too much for me while reading. Now it makes circa 9 hours.