Sorry for the late reply, but I am having quite some problems with my eyes unfortunately.
First of all, introducing such a feature via new code, now that I think about it, MIGHT be superfluous. I seem to remember a way to "attach" a familiar to an outfit. Someone care to refresh my memory?
Second, I do not think that there is an easy way to define the "optimal" familiar for each quest steps, nor that such behavior is actually needed. I've been reviewing my auto ascension process occasionally, and Mafia usually looks for three things: more MOX, more meat and some items.
To keep the process as clean as possible, I would use either the Bandersnatch with the appropriate jub-jub bird or the sandworm (effortless spleen items) for the first requirement and a fairychaun for both the second and third.
I guess that, putting it in simple words, a way to change the familiar equipped based on what the script is trying to do (giving the player the option to set up the familiar/task relationship) would be a great thing
Also, I may be sounding a little too critical, or spitting in the plate I'm eating from. Let me assure you that this is not the case. I respect your awesome skills in creating such a script, as much as I respect Zarqon and all the authors of the scripts I use. Kudos to you all