Kev, but... how easy is to actually remove a valve from a rim adapted to tubeless tyres? I understand they are fitted at pressure in the rims and not really easy to take out. Also if you need to fit a tube roadside you are going to need some strong tyre levers with enough leverage length to pry the tyre off the rims and capable of wedging it back in. To my knowledge people with tubeless tyres carry those tyre plugging kits consisting of that corkscrew tool and the rubber plugs + glue.