Mapping between Currier A and B

[nablator]

There could be other substitutions worth commenting upon, but my main interest now is understanding how to proceed. A possibility could be re-formulating this search into something like "simulated annealing", rather than this simple brute-force approach.

You need to investigate multiple substitutions at the same time. One substitution at a time may not be enough to detect an improvement in your metric. This of course makes the search space huge. I would try to "hill climb" first. Some problems are well suited to the hill climbing algorithm (just swap the target part of two randomly selected rules or enable a rule and disable the other and retest: if the result is worse, backtrack). If you are out of luck you get a different sub-optimal "solution" each time, and you need a better algorithm.

To reduce the set of possible sets of rules to apply together, this can be taken in consideration: a rule like "or -> edy" cannot possibly be right without another rule something -> "or" because "or" must not be eliminated from Currier-B. So you need a set of rules in cycles: pattern 1 -> pattern 2 -> pattern 3 -> ... -> pattern n -> pattern 1.