I moved the battery in my RX-7 from the engine bay to the storage bin behind the passenger seat.
What I did was install a battery tray with tie-down in the bin, then ran a wire from the battery to the starter, and continued it from there to the underhood main power block.
There should be no need to fuse the line from battery to starter. Just ensure the wire won't rub on anything that might chew through the insulation. Use rubber grommets where required.