Form Display Rule to set values to default/blank?

Could a Display Rule (as in Show/Hide, Require/Do Not Require, Set to Blank/Default Value, etc) for Forms be added to revert field values to either their default or blank value? For example, with a labor tracking app, each labor record can have either of 2 possible number values (flat rate or hours), depending on the value of a prior dropdown (billing type : flat, hourly). An example of the issue I am currently addressing in a seemingly clunky manner with table rules is when a user selects hourly, enters an hourly rate, and then switches to flat rate, and also enters a flat rate and both values are stored. I want to be able to force the unused field to blank or default (also blank, in this case). I have similar situations in a multitude of places, and this one change would eliminate dozens of table/form rules for me, and save me loads of time. Thank you!