It occured to me that two of the most critical dimensions for folding bikes are wheelbase and reach. The former being the most crucial since it can often not be altered in any significant way. Also wheelbase can have a huge impact on handling, speed and comfort, possibly even more than wheelsize. Perhaps we can make a list of these measurements for folders (in their stock form). For the wheelbase i suggest two measurements, Axle to Axle distance and possibly Rim edge to Rim edge (to discount tire variations).
I for example was surprised to learn that both sizes were slightly greater on the 16 inch Brompton than on my 20 inch Twenty.
For reach another three measurements perhaps. Minumum & Maximum extension. Distance of stem to saddle when they are in stock positio, perhaps a range etc.
This is a lot of sizes, but i for one would value axle to axle lots already. Some of the bikes i'd like to know these sizes for : Breezers, DT's, Dahons, Brommies, Twenties, Swifts (is already online right?) BF, etc etc.