Since there was talk of modifying the handles to be able to change to different stones on the same handle. Maybe you could look at making them longer and or /wider. Most full size stones are much longer and since the Shapton / Chosera stones are cut from the full size stones there will be less wastage. Maybe optimize the size to limit offcuts from the full stones. This will also allow for more upstroke/downstroke per pass. Most guys have quite big hands and even on most videos the handles look positively small in some people hands.
Cost of stones should not really change due to less waste.