Sending email as alias in office365?

It's great that experienced techs here are giving it their all, but this situation clearly isn't ideal for a stable and reliable IT environment.  Just because one can use workarounds to do something, who's to say Microsoft doesn't put out an update to one of the many contributing products in this equation that renders the workaround nonfunctional? Meanwhile you've assured your executive team this can be done. 

Any IT manager will tell you, better to say it's not possible than to promise something you can't sustain, and based on the varying responses to many people doing some of the very same steps here, it seems it's not something consistent across all editions/setups.  Besides, surprisingly, nobody has mentioned the simple option of just adding an email-only Office 365 account:  for CAD $61.20/yr. (USD $45.50) you can get Exchange Online Plan 1 for a user and just be done with it.  I'm certain the time you've put into figuring this out plus dealing with future glitches costs more than this, even if you're talking 5 or 6 such accounts.  If you have to do this for 100's of users, good luck with the distribution list thing  ;)