To aid with blow outs you could consider fitting runflat tyres, some control can be retained. Why have the german car companies lead with RFT tyres across their ranges? Either way 70mph/100 mph a blowout isnt going to be fun.
Have you ever driven on an autobahn, the level of driver courtesy and awareness is much higher than in the uk where every other drive is a lemming. They generally keep out of the way of fast moving vehicles.
If the cars are not roadworthy for 100mph why are they roadworthy at 70mph. Even a basic modern car can exceed 100mph, should MOT's be more strict to remove the old bangers off the road?