Provide drill-down menu functionality as an alternative to cascading drop-downs

Allow a user to populate a lookup list or choice column in a particular format such as: 
Option1_Option1.1_Option1.1.1 
Option1_Option1.1_Option1.1.2 
Option1_Option1.2_Option1.2.1 
Option1_Option1.2_Option1.2.2

This could then be rendered in a drill-down control allowing a user to browse for the item they require using one 1 control instead of using a series of linked drop-downs as per the following example: