On my Sony Nex-7, I could specify MF-Assist on a buttom. What it did was wonderful:

You press it,get your magnification directly and when you released it, you had the full Picture back. Very quick process.

On the Sony A7R: No way. You Need to press the buttom, you get a useless window which you could in theory move around to magnifiy a different area, than you Need to press again to get magnification and than you Need to press two times more to get back to the original overview-Picture.

WHAT A MESS !!!!!!!!! PLEASE, PLEASEadd an an Option like with the Nex-7 !!!!!!!!!!!!!!!!!