Perhaps sodium lactate combined with a steep water discount? I'm thinking it would address the issue of the soap taking longer to get firm and maybe speed up the evaporation of water from the soap(since there would be less water to be evaporated). I wouldn't, however, do anything towards the end of making the soap milder any faster. That, I'm afraid, can only be accomplished with a sufficient curing time. I usually cure all my soaps for six weeks, sometimes longer for certain recipes. Of course I always make extra bars that I can "evaluate" during the curing process. And by "evaluate" I mean I can satisfy my impatience and need for instant gratification. Yes, I was that kid who always knew what he was getting for Christmas ahead of time because I would find where my parents had hidden the wrapped presents, slice open the tape with an x-acto knife, examine the contents, and carefully re-tape the package so my transgression would never be discovered. I never did get caught, lmao!