Simplifying a microprocessor controlled MOSFET switch
Why not use a relay - it can be driven from the 5V logic, possibly with a transistor to help it and the relay contacts would just connect in parallel with the load. What you haven't said is how fast you need to do the load bypass switching (is there any PWM involved) and what the maximum load current is - this may drive you down the MOSFET route.

Here's the relay I'd consider if it is just to act as a dumb load on/shunt switch: -



BTW - in your 2nd circuit there is no gate over-voltage protection when the power supply is greater than 20V (most MOSFETs can deal with maybe 15 to 20V on their gate but not 50V).