this is precisely why a turing complete scripting language is a bad idea in the context of cryptocurrencies: it is highly non-trivial to put bounds in place to prevent or mitigate exploits.
satoshi designed the stack engine for a very good reason. it doesn't look like this will ever be done in bitcoin itself. the risk is too high for that kind of experimentation to occur now. overall the system/network has probably much more inertia than initially thought. from which I infer that there will be several serious candidates in the long term.