Your question got me wondering just what was the sg of a bouché.
Seemed like a good excuse to pick up a bottle from the Beer Run. They had some of Etienne Dupont's 2007 Cidre Bouche, which is very tasty. On the label is says "All apples, predominautly (sic) Bisquet, Juretta, Avrolles, Frequin varieties are fully organic". The SG was 1.020 - not much less than JKS, but it tastes a LOT drier. The wild yeast definitely comes through, with lots of apple and a just a little bit of a brett taste in the background - overall it is very nicely balanced and carbed very strongly. I drank most of the bottle Friday, just opened the last of it and it still had a strong pop and good carb.
I like wild yeast batches crashed at 1.020, and they are not far off this, although my brewing friends keep cajoling me to go lower. So far the best one has been at 1.014. The wild batch I started a couple weeks ago got away from me - I crashed it at 1.010 and it tasted great, but I accidentally froze it halfway solid when I crashed it. I didnt have time to wait up for it to thaw so I racked it the next day, and by that time it had not only thawed, but since it was still on the cake, the ferment started right back up and took it down to 1.002, which is barely drinkable and way drier than I like.
Your brother might want to check out the Aspall organic and Samual Smith organic. Both are about the same sg as the bouches although the wild yeast taste isnt as prominent. For those, you could get close to the style by using fresh juice and an ale yeast on top of the existing wild yeast (dont pitch k-meta), so these would be easier to reproduce something close or maybe better.