Not sure if this would be possible but maybe something to consider.
Would it be possible to have a setting for applescript widgets to only if visible and specify how often while it is visible?
Perhaps in addition to the settings: "execute every x seconds" (working whether visible or not) and the "always run when visible", have another setting for "execute every y seconds while visible".
That way a widget hidden in a group or with a modifier key wouldn't be running constantly, but could run repeatedly while the group is open or the modifier key is held down?