Our Santorin already had a watermaker added (with an engine driven HP pump). An additional hole and seacock had been added plus a magnetic drive electric boost pump. I can't suggest how else you can pick up sea water. The toilet sea water is inside the watertight cabins, so that's a negative, and I wouldn't want to feed off the engine sea water pick up.
Ours is situated in line with the shaft generator pulley on the centreline of the boat tucked in close to the engine mounting frame ahead of the Vetus exhaust box.
I agree about not putting another hole in the boat, but it has not been an issue. It's 3 thru hull seacocks compared to 8 in my previous 37' production yacht! And I guess the SM has that 3rd hole for the sea chest intake, or does that provide the engine raw water intake as well?
Ocean Hobo SN96