One/Alex + NAS library + Spotify + TuneIn - How?

Our existing Play1, Play5, and Bridge happily play our music library from an NAS drive attached to our airport wifi box and router. Spotify and TuneIn work too. Now we've added a One with Alexa for the kitchen to use voice control to switch between our three "sources" of music, but cannot figure out how to add the NAS as an input.

We've been through the setup, updated all versions of the Sonos App updated the Sonos software, installed the Alexa app and been through the setup steps.

Is this just not possible?

Each version of the sonos app (mac, iOS) stores the path/credential info for our NAS. I'm no engineer, but couldn't that be stored in my Sonos account (which the One/Alexa is already linked to) so the One/Alexa could look it up and play our music library from it?

Thanks!
Hi

Unfortunately Alexa doesn't support the initiation of music from a local library via voice control. You can however start the music from the app and then control volume, skip to next track, repeat track, etc via voice control. The other option is to load your library into the Amazon cloud and then have full voice control - it will search your My Music library before searching any streaming service that you've setup. (This is at a cost though! 😞 )

The Sonos skill cannot access anything on your local network, so this wont work. However my Skill can do this, check the Skill Store, if you want to play files from your NAS by talking to your Alexa.

Thank you to UKMedia & Controlav for your quick replies. So far (as of Dec 2017) the solutions seem to be:
1. upload library to Amazon Music (with subscription cost) which makes it, in effect, a stream Alexa can control
2. try a 3rd party Alexa skill like ControlAV
3. use Sonos app to launch playlists of NAS music, then use Alexa to start/stop

Other suggestions I've received:
4. Wait for Google voice control on the One (promised for 2018), then upload library free to Google Music (similar to #1)
5. Wait (perhaps forever) for Alexa to talk to Apple Music then upload library there (similar to #1)
6. Stick with non-voice Sonos units and attach an Echo/Dot/Google Home Mini (2018)

Unrelated, but perhaps useful to others:
Not being able to change the 'Alexa' wake word is actually proving a real problem, as in this home the number of friends and family members named Alexis, Alexa, Alex, and Alexi is large enough to prevent regular conversations from triggering the speaker. For now we may have to switch for another Play:1 and stick with the app for control.

Thanks.