As noted, this should really have been in the plans from the beginning. My feeling was that most cars of this size were sold in estate form and with the bigger engines so I decided to do a bit of research based on the number of post '07 BMWs and Audis for sale in Switzerland using 'autoscout' a site which lists almost all Swiss cars.
With Audis the number of A6s is in the ratio 1 saloon to 3 estates.
In BMWs range there are more saloons sold with 2 saloons for every 3 estates. Autoscout enables easy searching of BMWs by engine size. For the 4 cylinder cars the ratio is the other way around with 3 saloons for every 2 estates, but the 530 (petrol and diesel) seems to outsell the 520 (petrol and diesel) by 5 cars to 2. The 525s are 50% up on the 520s.
As an aside, there are as many '07 on RS6 and S6 Audis for sale as 520s, and most of those are Avants.