I'm sure it wouldn't be altogether impossible to come up with a MCB or similar unit that could check the integrity of a ring and cut the power if it was not intact.
It could be done electronically by simply sending either a continious or intermittent signal down one side of the ring and if it doesn't come back on the otherside trip the MCB. Similar technologies exsist for controlling lamps etc remotely via piggybacking signaling onto the power system of a house.
Generally, unlike radial installations there are only 2 or 3 rings. So it wouldn't be economically prohibitive. They wouldn't necessarily have to be on the fuse board either. You could wire them in after it across the 2 X L and 2 X N of the ring (perhaps the earth integrity could be tested too).
Such a system could be made to fit into a standard DIN rail consumer unit.. even if it occupied a bit more space than a MCB..
It would be a pricy sollution but then again some people considered RCDs excessively pricy and unnecessary for years. If it prevented house fires it might be worth it.
Then again how many broken rings have caused house fires?
DIY jobs on radial circuitry is often just as fire-prone.
