Would be nice to have radio buttons in the GUI. They would have to be grouped, so that when one is selected, the others are deselected.
The DS ports would benefit from that; it currently fakes radio buttons in its options dialog by using checkboxes and lots of code which "manually" deselects the other checkboxes in the same group (the groups being hard coded, naturally...). See also dsoptions.cpp, e.g. DSOptionsDialog::handleCommand() in there.