If a child theme is installed later, copying all options from parend to child can be pita. When acivating a child theme which has no options saved yet, ask if copy from parent.
Oh how I wish this was possible. If the theme is using the Customizer, there is a small workaround, but it'd need a plugin .. yeah, I vote for this! Eg. as a simple filter or action hook, or a function call during theme activation.
This is possible to do inside the theme with a filter on after_switch_theme or inside an activation hook.