I would like to see the possibility to simply add users by name. 

Adding by e-mail, Login ID or SIS-ID (!) makes no sense to most non-admin users, and makes an otherwise nice feature cumbersome for teachers who would like to add other faculty, TA's and guests.

Regardless of method, an automatic lookup in the database as you start typing would be helpful as well. A feature which is already available in other parts of Canvas (e.g. when assigning assignments to users). 

Hopefully this is an easy enhancement which will ease the load on local Canvas support.