These acronyms kill me sometimes. GVT = German Volume Training?
I know I've been promoting this workout a lot lately, but you may want to try the Ed Coan Peaking Cycle. I was looking to do higher reps for a bit, but then return to low rep again. I believe it's designed for bench press, but I'm actually using it for squats, deadlifts, and power cleans as well. Here is the link:
Powerlifting Heads-Up Ec Coan Peaking Cycle Calculator
On the Coan cycle, I do assistant lifts at lower rep/higher weight when I am on the first weeks doing high rep. For example, if I'm on week 1 doing Bench Press, I'll do SOHP at 3 reps at high weight. Towards the end such as week 12, I'd do SOHP at 8-10 reps while doing bench at 2 reps.
As far as the German Volume Training, I'd be worried about starting it then realizing it's too much then being back to square 1. From what I read on German Volume Training, it seemed like way too much volume and would be hard to realistically fit in many people's schedule.