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the security features of Marlin may not affect the external mosfet and the heated bed gets full current without temperature control

Worst case the MOSFET fries and gets stuck open and the bed constantly draws current, I don't really think Marlin can do anything about that. You would get it an error, but the bed will continue to draw current as the MOSFET wouldn't be able to switch off.

Replacing the terminals help, although I don't trust the traces either, but everyone isn't going to be comfortable making such a modification. An external MOSFET is probably the next best thing.

You can also have some form of automation with an external MOSFET. For example, in my case I have an external MOSFET and I am using relays to control 12V power to the board and the MOSFET which is controlled by Octoprint.

This way if the MOSFET dies and is stuck open things will get too hot, then Marlin will trigger an error then Octoprint will disconnect turning the power off relays.

I also changed the hotend from a 40W cartridge to a 30W cartridge. Max temp will potentially be lower, but theoretically the 40W cartridge can get hot enough to soften, or maybe even melt, the aluminum.