One thing that I don't understand, not even a single little bit is this addon rubbish that P3D introduced and now we have a thousand folders with ten thousand files all over your hard drive with NO control over them whatsoever.
Before, you had thousand folders with ten thousand files polluting your simulator folder, which was obviously worse and made reinstalling very difficult.
Since ORBX went this route as well, the Vancouver airport is a mess. LAX is a mess
If OrbX causes problems to other airports, it's not because the files are installed "outside" the simulator, but because the way they products are made.
and we have NO control over the layer priority of files - as a matter of fact, I don't even know where to begin to have the FSDT airports on a higher priority as the ORBX ones especially with ORBX's terrain scenery like Canada/Alaska, North and South California.
Yes, you do, if you have the Lorby Addon Organiser. Always places airports on top of everything else. However, sometimes it's not enough. At KLAS, for example, you MUST use a fix made by OrbX to fix the problem they caused to the airport, which couldn't be solved "just" with setting the priority.
I'm using Addon Organiser but every time you run ORBX CENTRAL then everything is back to where it was before.
So your problem doesn't have anything to do with FSDT, P3D4 vastly superior add-on.xml method. It's just a matter of OrbX forcing itself on a specific layer. Is that one on top of other airports ?