If it had been exploited in a 0-day fashion, significant & widespread losses (due to acceptance of counterfeit BTC) would've been likely,
I am weary of this assertion. Many bitcoin related businesses use custom implementations of Bitcoin that are based on the underlying consensus rules. The same is true for the miners today (even if they broadcast they are using other implementations), so I doubt a single malicious actor could have gotten counterfeit BTC more than a small number of confirmations.
I would echo what DooMAD said in that the solution is to encourage more implementations, and for each implementation to not have a high percentage of overall nodes.
At the end of the day, the Bitcoin network is nothing more than a bunch of consensus rules that everyone follows.
What many people do not realize is that having people run different implementations makes it easier for attackers to partition the network and thus harder to resolve situations where vulnerabilities are exploited. Network partitioning can cause multiple blockchain forks which is a much harder situation to resolve than a single fork or an entire network shutdown.
The solution to this is simple, and it is that the blockchain (whose tip contains the most cumulative work) that follows all of the consensus rules is the Bitcoin blockchain, and any fork of this is not (in many cases, it would be an altcoin intentionally created).
The incentive to attack an implementation that is used by 10%-20% of the Bitcoin network is much smaller than the incentive to attack an implementation that affects 90% of the network. The further would be a minor hiccup, while the later has the potential to actually steal large amounts of money, and cause serious disruptions.