Hey, so I realize this is an old post, but in case you're still interested I have an idea.
In the app IFTTT you can create an applet to send a command to Alexa.
IFTTT doesn't have manual shortcuts or a trigger for SleepAsAndroid, but you can set up a trigger to activate when Automate posts a notification with specific text in it, like "RunAlexaRoutine" and then run a service like "Alexa Actions by mkZense" to send a command to Alexa directly.
Then you can just set up an Automate flow to post a notification with the trigger word when the alarm goes off, which will trigger the routine.
If you've never used IFTTT or need help let me know.