FS2004 SDK (BGLCompSDK p.11) ... What is that?
The FS2004 Software Development Kit ... supplied by Microsoft ... still to be found here
https://www.fsdeveloper.com/forum/resources/categories/fs2004.6/
SceneGenX implemented the "generic buildings" aspect, not sure if anyone else did.
I use it extensively, in a basic manner, but quite sophisticated results can be achieved, with a little effort ... see
https://www.fsdeveloper.com/downloads/generic_buildings_for_FS9_and_FSX.pdf
Afterthought :-
I've had a quick look at ADE (not a program I'm familiar with) and it does indeed have some "generic building" capability, but only, as far as I can see, to the extent of a preconfigured set of buildings, which I can adjust for size, but not the texturing.
SceneGenX allows me to "design" a generic building from the ground up ... bottom layer, middle layer, top layer and roof ... and apply texturing to each layer separately.
In a very basic scenario, say for a 20m long building, I might apply a texture at it's default (256 pixel) setting, but if I wanted a similar building 40m long I could apply the texturing at 512 pixels and end up with the texturing LOOKING THE SAME FOR EACH BUILDING, just twice the amount of windows (or whatever) on the second building
In the attached example the right-hand building is 20m square, the central building is 20m x 40m long (with the same texturing doubled for the length on the ground floor only), the left-hand building 10m deep by 20m with the same texturing halved for the depth.
The range of available texturing isn't extensive, but adequate, with a bit of imagination.
If you delve into the depths of ADE you may find similar functionality ... my brief excursion proved fruitless.
SceneGenX can be used simply as a "building developer" should you so wish, thereby retaining your familiarity with ADE.
Further afterthought!
Browsing the ADE User Manual, it's apparently not possible to use ADE to design generic buildings from scratch, but you can import pre-designed generic buildings, so you could use SceneGenX to to develop custom buildings (in some remote corner where they won't get in the way of anything), then import those results into ADE, which you're already familiar with.
Sounds all a bit long winded, but if you've got repeated need for basic custom buildings it might be easier than trying to come to grips with one of the model design programs.
Hope this helps