Towed with A4s, three A6 Avants and now have a Q5 - al of them have been very good tow cars - essentially with the 2litre tai and autos. I expect the A7 will be just as good probably better. I was looking at a A7 when we decided on the Q5 - we went for the higher ride - easier for me to get in and out of. (replaced knees).
Oh and PS the indicators worked on all of them!
As far as I'm aware the Audi A7 shares most of its underpinnings with the A6 estate, and quite a lot of bits with other VW group cars all of which are well-regarded as good towing vehicles. So it should be fine (provided of course that the caravan is well-matched).
------------- "Don't wait for the perfect moment. Take the moment and make it perfect."
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.