I wonder if it could/should be adapted to work for fuzzy queries too. Conceptually it is the same thing - given a user's vague input you try a number of variations on their behalf and focus in on the most likely interpretation. With multi-match you vary the choice of field context and with fuzzy you vary the choice of word spelling but the objective is the same - how do I use the index's term stats to select the most likely interpretation of user input?
Lucene's FuzzyQuery has been broken for many years because of the IDF bias. I tried to fix that in FuzzyLikeThisQuery but I think you have it right here in rewarding all variants based on max DF rather than what I did with averaged DF - you pick the reward based on the most likely interpretation.  Here we also added a slight tie-breaker bias to improve focus. Admittedly "fuzzy" brings edit distance into the ranking equation but I feel it should share the same IDF blending policy implemented here.