Short of joining to a dimension table to get a member's description, is there a way to configure the blend table build process to use a member's description (alias) instead of the member name?

You could use the Star schema parameter in the BiBlend config.  This will create member tables containing description and a few other attributes.   The star schema setting will also create a view which you can reference in the app.

In my case, the view wasn't quite what i needed  so I created my own based on the fact and member tables created by BiBlend.

Ideally I would have liked to have used the member table but being on Azure created problems as I could couldn't query across databases.   On Prem shouldn't have that issue though.