Interesting comparison and pictures OP. However, I don't see the viability of a secondary chain being alive long enough. The issue that I see is that a duplication of the chain, and a situation in which both are alive, would cause tremendous chaos and most likely ruin Bitcoin. I think that it is in everyone's best interest (including the people led by greed) to avoid such a situation (excluding the people that are trying to ruin Bitcoin).
There is no need to worry about that. If the longest chain is 75% of the total hashing, miners will will converge.
Your percentage is trivial. I wouldn't consider 75% consensus.