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 potentially point the datasource to get the descriptions instead of the labels, but then you need transformations rules for that too.
You can of course point your data source to get whatever into the Accounts, but bear in mind that if you are doing any type of aggregation on accounts that will not work with anything besides the true account labels.
you can easily build a view in SQL to be very generig to always return the descriptions instead

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.