He has a twin engine cruiser. I think I see where he is coming from. He wants to install valves at deck level so he can switch from seacock to bilge without lifting a hatch
To answer OP's question.
1. You wouldn't want to install that long of a loop in your cooling water intake. If you get airlocked you just burned up an engine.
2. The water pumps on your engine are small, this has been discussed before. It's not that the idea of using engines as crash pumps is a bad idea, it's that adding a backup large capacity bilge pump
on a second, (higher) float switch will remove more water. And have less risk of sucking c%^P into your engine.
3. Crashing into things that hole you under the waterline is a rare event, (hopefully), engine water pump problems,....not so rare.
Back to question as mentioned above for maximum effectiveness you would want to tee right at the seacock, through the valve then directly to bilge under engine cavity with a screen
If you have water coming in, you need to be in the engine room/compartment shutting off seacocks, and finding source of water anyway. Also have plugs made for each seacock, so when, (not if), the "stainless" pipe clamps rust through and the hose pops off the seacock that is rusted open, you can stuff in the plug
you tie wrapped to the seacock in the hole and limp back to port.