Of course, masterbatching will fly, especially if you use only one recipe. I could not really masterbatch my oils other than in individual buckets for batches because I had 2 main recipes, a vegan and non-vegan that I used. Also, I would tweak my main recipe soft oils depending on what I purchased in bulk when I did my oil runs. My trick was my stock was kept up to date so I would only have to make 4-5 batches a week to restock even when I was doing 4-5 markets per week, but I also carried a min of 40 different scents so I always had a wide choice of soaps to sell, so I did not have to crash and burn making soap. I just liked to pick up a bucket that was ready to go just having to add in my lye, liquid, and any additives I wanted to add to the particular batch. I just never found it any easier to measure out oils in one 5 gallon pail as in individual 1-2 gallon pails, but that is me. Plus I do not have to worry about my bucket of oils solidifying, but if they do my pails fit in the micro.
As for adding SL to your masterbatched lye I do not think I would, but I really do not know. I soap with vinegar and I will mention you cannot masterbatch lye with vinegar.
I am a little late to the party with this post but I started it a few days ago but had a Gecko emergency.