I'm not sure why you're shying away from using AppleScript - it works just fine, and as others have said, it's extremely unlikely it will go away. And if you've already been using AS for QK, I think it's a no-brainer.
As far as FMP and KM URLs not working, I've got other apps that have the same issue, unfortunately. But maybe you'll get lucky and the FMP developers will listen to you.
If you'd rather go some other way, you could consider writing "trigger" files to a folder, and have a macro that triggers when files get added to the folder. You could have the filename be either the name of the the macro, or the UUID. I'd prefer the UUID, since it's unique, and will always be a valid filename. If the macro requires a parameter, you could put that in the file's contents.
So basically, FMP would write an empty text file (or whatever) to a specific folder, and name it the UUID of the macro to run.
The macro monitoring that folder would get the name of the file, delete the file, then run the macro.
I assume you already know how to launch the desired macro, but if not, this can get you there (this works with UUIDs also, in spite of the name):