FCPX Audio MIDI Setup & discrete mono multichannel "surround"

I'm running FCPX 10.2.1 on OSX 10.10.4 on late 2012 iMac (3.4GHz Intel Core i7)

I have an FCPX project with 9 camera "angles" and editing in realtime using Multicam editing with proxies.

The video playback framerate is workable.

I'm using an Apogee DA-16X (good DACs) with Firewire card for realtime audio output to at least 8 discrete audio channels.

Each of the DA-16X analog outs is patched to a discrete active speaker that is arranged in an octagon.

I will ramp up to 12 channels when I can sort out the following issue:

Audio MIDI Setup 3.0.6 (and System/Sound) see the DA-16X. Good.

I can choose "Apogee Firewire" and see the 16 output channels. Good.

I can select "Configure Speakers ..."/Multichannel/Geometric/Octagonal and map the speakers and they tone test properly. Good enough (for now).

[This isn't anywhere in Apple's help as far as I can see]

Meanwhile in FCPX I have my 9 camera multicam.

Let's say, to begin with, I need to map each camera angle (=locked in video+mono audio) to a DISCRETE audio output channel.

[I could ditch one angle for now and would be happy if I could just map 8 channels to my octagonal speaker arrangement as allowed by Audio MIDI Setup).

Am I wrong in now thinking, after much poking, that this is impossible?

FCPX is limited to 5.1 Surround and is doing encoding and I can't simply map each track/channel (=camera angle) to an individual output. Right?

I need to use a DAW, say Logic, wherein I *can* do the track mapping to appropriate outputs and do a time-sync'd video playback?

I would really like to stay within FCPX and achieve this.

I'm guessing AVID Media Composer could do it?

I am assuming that I can maybe generate a Quicktime with, say, 12 channels of audio and have the MIDI mapping integral to the file? Haven't got that far yet and I know that would require a DAW or some serious Quicktime audio fiddle.

What I need to be able to do at the moment is edit and playback with my deliberately funky surround audio arrangement.

Seems like this is what Dolby ATMOS would resolve if implemented in FCPX. Please?

Having FCPX restricted to 5.1 seems so 1999.

[Or somebody tell me I'm missing something, that would be great]