That's great is finally solved.
High load devices need relays using full battery power / triggered by small wire & load switches at long distance.
Picture the main battery & switches sitting next to pump.
If switches can handle the load of the pumps - fine.
But that's not the case - switches have very low load ability in that amp range.
They would get hot & melt.
You could use phone cable as the trigger voltage to the relays & relays would have the 10G wire to run the pumps.
Of course - the relay's main power source would also need 10G wire from battery.
Similar to key switch to starter - it can be any distance from starter - it's just the trigger voltage going there.