It depends on where you need to see this checkbox. Use icon facet for panel menu and it will be at icon location or just place as nested component and it will be placed together with label.
For simple toogle panel - the same. markers facet or header facet..
You may ask why would I want to do it. Well I tried to do a rich:tree with chechboxes in nodes and leaves. It proved to be a total non working failure. I managed to get the checkboxes in nodes and leaves. But I wanted also to check all child nodes when parent checkbox is checked. This is not possible because the rich:tree would not rerender on checkbox change.
So instead I'm investigating to workaround
It seems you too categorical.. all will works as it should when well designed.. I could tell you that rerendering of leaves is possible without any problems.