Couatl.exe is needed by the scenery, since many months already.
There's no advantage whatsoever disabling it for memory footprint reasons because, the memory taken by Couatl, has been saved in the Addon Manager, which is now leaner than it used to be, and it does less tasks.
Instead of worrying about the 25MB that Couatl takes, which is not much compared to the roughly 1.0 GB FSX total with a simple default airplane, you should be worried about CPU usage instead.
Since Couatl is an external .EXE, it's automatically offloaded to free CPU cycles by the OS, and on multicore machines, there's plenty of it available and not used by FSX itself so, the more we do with Couatl and the less we do with the Addon Manager, the less we risk slowing down FSX, because an in-process .DLL like the Addon Manager *can* slow down FSX, since it runs on the same thread, for several reasons related to thread safety. Not to mention that, in case Couatl crashes, the worse it will happen is the scenery will disappear but, it the Addon Manager crashes, it will bring down FSX with it.
And, speaking about CPU usage, here's a screenshot of Process Explorer monitoring the Couatl program, with FSX parked at PHNL so, with all Couatl features (ParkMe, YouControl, the PHNL Digital Clock, etc.) enabled:
0.00% CPU usage...
