Welcome. Sorry to hear about the 2014 FX4.
Sorry I have no info on a potential bad splice.
The seat trim and controls look identical to my 2004 Eddie Bauer so maybe they only changed the seat itself and not the base.
So the wires for the power mirrors run through the driver seat. In fact the driver seat module(DSM) handles memory for the mirrors, and obviously the seat controls. I'd check the fuses first if you haven't. Then for the mirrors make sure they connected in the door. The interior door cards are super easy to remove on these. Once you do one the other will take 5 minutes to remove. You'll need a 7mm socket, philips head screwdriver, I think T30 torx and a dull knife or plastic trim tool. Pop the 7-8" or so long trim panel behind the arm rest off, it snaps on. Remove the plastic door handle trim from the front, it also snaps in. Then pull the window and mirror switch panel up. Now you can verify the mirror switch is connected. Once the screws are all removed lift the door card straight up and off, there's another connector up by the sail area.
I don't think the pedals are wired through the driver seat though. The common issue there is the brake pedal stops moving due to a gear that splits. In this case the throttle pedal will still move. You can remove the cover and manually turn the brake pedal to the preferred location. If there's no power make sure the motor is connected.
If the mirror fuse and wiring all checks out and the seat also has not power I wonder if you might have a DSM fault.
A rather high end OBDII scanner will help you troubleshoot the mirrors, seat and DSM. Might even help with the pedals.
