there are a number of ways to do this
but its down to the power rating of the latch switch
if you take the positive from the battery to the switch then to attey ok good but the switch must be rated for the power of the battery's in amps, not voltage so let's say 30amp can it do that?
ok so you will need say 30amp plus cable, not solid copper but proper braided silicon cable, mains voltage cable is for voltage, not amps it will do the job but its solid copper it breaks gets hot and is for your house, not a mod
you have got the right idea a MOSFET will protect your fire button via its gate and will stop reverse polarity but won't stop someone sticking a uber 0.0000000000003 coil in the attey and going "look at me boom"
to wire up the led light on the switch you need a resistor to drop the voltage from the attey to the led it will work for a while without one but will die from heat in a day or 2 this is wired from the attey NOT the battery positive to + negative to minus -
you are on the right lines
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