Using your example: for a while HTML was defined by Netscape but that did not save us from the Microsoft fork.
Hundred pages of standard did not work there either.
What might work is a set of test suites that major implementations and new releases have to pass. I am willing to contribute to such.
Diversity is good and may help discover issues. But as Gavin was saying and as I like to point out: The most dangerous kind of failure in bitcoin isn't an implementation bug— any blockchain validation inconsistencies in widely deployed implementations are significantly worse than pretty much anything other than a full private key leak or remote root exploit... and are even harder to avoid.
There are many useful 'test' cases in the mainnet chain and in the testnet chain, but those only test valid blocks. Bugs that accept thing which should be rejected wouldn't be found by those. Matt has been working on a test feeder tool as part of his effort to make full node support for bitcoinj which is very promising. There are also tests included with the reference software. There needs to be more of them.