Add back a downtown circulator bus.
This hasn't been successful in the past, but now (especially with the failure of the urban rail vote, which would have connected several downtown destinations) perhaps it's time again.
With the planned significant expansion for metrorail, as well as the new downtown bus only lanes, a circulator might see more success.
For instance, a loop from the planned downtown gateway station, up trinity, across on tenth, down Guadalupe, and then back east on 5th. Especially if bus-only or bus-only-during-rush-hour lanes would be added to those segments currently lacking them.