Great news: this feature has just landed 
You can now set target costs per beer, schedule them from a date, and see actuals against targets on every batch cost report, across batches on the new COGS vs target report, and in the margin reports. You can read more and find the help guide in the announcement at Target costs are here: set what each beer should cost, and see where your batches drift from it .
Thank you to everyone who was involved in this thread and voted for it!