Stereo sounds in FMod would be a mistake I think. My brother played with twin-engines to recreate their separation but it causes other problems.
Stereo wav files are not the same as 3D effects. in FMod you can change what is heard by distance and angle from the source. The Lancaster, C47, B17 and I think B29 are examples of what can be achieved and I think a lot more is possible with more time.
The startup sounds were a mistake. Rather than poop on the efforts that were made why not just use the defaults or start your own sound project. I think anyone could directly input a previous sound pack and make it work with FMod. It wont be as good as one that uses FMod as it is intended but its also not hard to do.