Currently the aircraft library is a mix of enhancements to built-in planes and portovers from FSX. Eventually, once the SDK matures a bit, we should start seeing some native MSFS planes available as freeware as well.
It would be awesome if there were multiple aircraft categories, so that downloaders could tell if a plane is truly MSFS-native, a possibly tweaked portover via a porting utility, or a modification to a built-in plane. There's already the Aircraft Additions section, but many posters are putting their tweaks in the main Aircraft category, and many portover planes aren't clearly described as such.
Personally I want to stick with actual native MSFS planes, but that's a personal preference and many sim pilots are happy to fly portovers and don't mind the quirks. I'd just love to see planes clearly labeled as to what type they are. This will help avoid situations we see on older sites, where sometimes FS9 planes are labeled as FSX even though they have quirks that prevent them from working under DX10 or P3D. There are some authors, such as Rob Richardson, who are creating native MSFS versions of planes they've made for FSX/P3D, and it'd be nice for folks to be able to know those aren't hacked ports but true MSFS SDK planes when they become available.
Aircraft - MSFS native
Aircraft - Ports
...would be great.
Alternately, some kind of searchable "Verified MSFS native" metadata would be great.
Just a suggestion. Right now I don't think there are actually any native planes available outside of payware, but that will change soon, and being able to find those would be fantastic.