Q: How can I stop Final Cut Pro X telling me "incompatible audio units found"?

Update your audio units to their latest versions then force FCPX to revalidate.

See this post for details:

Re: FCPX: Audio Units (NI Guitar Rig 5) hangs startup

I've done some research and Waves AUs have been a pain in everybody's a$$3s. It doesn't behave even with a third party Audio Unit Manager app (like this one: http://audio-unit-manager.en.softonic.com/mac/download).

Since FCPX only validates once per update, try this:

Follow the steps here: Re: FCPX: Audio Units (NI Guitar Rig 5) hangs startup

Move the offending Waves AU out of the /Library/Audio/Plug-Ins/Components/ folder.

Restart FCPX and let it validate all the AUs left.

Move the Waves AUs back into place.

Launch the apps you need the AU to work in and check to see if they are included. (You might have to use the AU managers of apps like Logic, etc.)

Launch FCPX to see if it chokes on the validation.

You might have to do this every time FCPX is updated until Waves plays nice with the rest of the system.

This is not guaranteed to work (and FCPX changes from update to update) — but good luck!