So what options do we have in this regard? Fly without real weather and have couatl or fly with real weather and have no couatl?
You said that Active Sky "recommends" to launched FSX through it, but what happens if you don't ? Does the program stop to work ?
Forcing to start FSX as a sub-process of something else is a VERY questionable method, and I can't think of a reason why a program would absolutely need to do that.
If Active Sky still works when launched separately, you have the answer to your question.
Couatl.exe, of course, does the standard thing as suggested by Microsoft, which is using the EXE.XML file to let FSX launch itself, which is how FSX add-ons are supposed to be launched, not the other way around.