>> AFAIK MLD, LightHeart, and Alpinlite don't offer double-wall tents.
Yes, I believe they do. For the most part, their double walled options are for one person, but they do have double walled combinations for two people:
MLD: Duo InnerNet and Duo Mid. "Duo Combined with the Silnylon DuoMid = 2 person FULLY double walled tent for 29oz" (from http://www.mountainlaureldesigns.com/shop/product_info.php?cPath=35&products_id=127).
LightHeart: Duo. "A spacious hybrid (single/double wall) design" (from http://www.lightheartgear.com/LightHeart_Gear/Duo.html). Since they call it a hybrid, maybe it isn't double walled. Interestingly, they call their solo a double walled, so I would be curious as to the difference. Maybe their solo is double walled, but their duo isn't.
Alpinlite: Bug Shelter 2.0 with Terraform. "The Terraform tarp, available seperately, has been specially designed to work with this the Bug Shelter 2.0." from (http://www.alpinlitegear.com/index.php?main_page=product_info&cPath=12&products_id=50&zenid=b97ca17519065567e21567b3ee82e387). Despite the spelling errors, it looks like a double walled tent to me.
All three of these are designed to work together, as double walled tents (with the possible exception of the LightHeart offering, as noted). Oh, and I forgot another one (my apologies):
Hyperlite Mountain Gear -- ECHO II Ultralight Shelter System - http://www.hyperlitemountaingear.com/products/shelters/echo-ii-ultralight-system.html
This is arguably the most integrated and high tech version out there. To be fair, some of these might not have been offered when the testing began. But I'm pretty sure MLD has made a double walled, two person tent for a while now.