Yes, there is a way to do this but you are not going to like it. First make another xaml dictionary. In it define a style for each control in Aero or w/e theme you're using, then set BasedOn property to implicit key.
example
<Style TargetType="Button" BasedOn="{StaticResource {x:Type Button}}">
then create a setter for FocusVisualStyle
<Style TargetType="Button" BasedOn="{StaticResource {x:Type Button}}">
<Setter Property="FocusVisualStyle" Value="{x:Null}"/>
</Style>
Note: you'll have to do this for EVERY control.
Next merge your new themes dictionary into Window.Resources
<Window.Resources>
<ResourceDictionary Source="[your dictionary]"/>
</Window.Resources>