I think evolution can escape a local minima - however - I would imagine that most organizations aren't able to support the individuals who can lead an evolution

I think evolution can escape a local minima - however - I would imagine that most organizations aren't able to support the individuals who can lead an evolution toward a more long range goal that would require transiting the natural boundaries of a minima that an undirected evolution would naturally transit. With regard to your own project, I find it somewhat hard to believe that you can rewrite a 20 year old code base in just one year's time. Assuming an output of 50 LOC a day - and 250 work days a year - which means the system you are replacing is under 15k LOC.