Obviously, it would be much safer for a community to take care of one implementation with fewer lines of codes.
I think I can guess where this is heading.
That being said, having multiple implementations is good for the individual who runs multiple nodes with different implementations. With multiple nodes each with different software, attacks exploiting critical bugs lets them know if an attack is going on. If everyone ran multiple nodes with different implementations, then multiple implementations are fine. The network would not shutdown and there wouldn't be any network partitioning. But not everyone is going to do that.
Perhaps not everyone would need to. If we adapt theymos' idea that larger Bitcoin companies should effectively place a small percentage of their employees on secondment with Core, what if instead they ran a Core node but also maintained a second node with their own business-oriented implementation? Something that might focus more on features for merchants, for example. Then they can report any inconsistencies and issues like would be far less likely to go unnoticed for 18 months? I'm unsure how many companies it would take for the idea to be effective, but if it worked, that would help create a decent safety net.