Another issue to consider is cleaning your fermenters after a small batch. On a 10-15 BBl tank this shouldn't be a problem as it is easy enough to manualy scrub and reach everywhere. In my case I often ferment 15Bbl batches in 30 Bbl fermenters and when its time to CIP I noticed that I need to use more detergent and more hot water because the sprayballs on most tanks concentrate on the top quarter of the tank where your Krausen ring would be if you did a full batch, but on half batches the krausen ring is halfway to 3/4's down the tank and it doesn't get hit as well. Sometimes I have had to manually scrub which is a pain in the butt on bigger tanks, or I have run an Acid wash then an Alkaline. Using more alkaline with more hot water than usual seems to work as long as the beer hasn't been in the tank for several months. Just my 2 cents.
"You are what you is." FZ