In the Java client you can force a specific selection by combining the 'Predefined answers' and 'Default value' properties for the field. Both can be bound to a vRO action if you have a more dynamic setting.
By the way, the tree view is available in the web UI starting from vRO 8.1
That is fantastic news about 8.1! I will test the migration upgrade in my LAB when I have a chance.