Curious to know if the base front brakes could be 'upgraded' using the original base calipers, but moved further out using 'performance' caliper brackets and 380mm front rotors.

Would probably give *close* to 'performance' brakes performance, without the high expense of new calipers... if the base calipers will bolt up to the larger brackets, be aligned right and end up in the correct position...

Just idle curiosity.... I've heard of similar being done on other cars

 

I am 99% sure there is no way can you use the 355 mm calipers and pads with 380 mm rotors and brackets, they simply will not fit even if you figured out a way to mount the brackets further out. To upgrade the front brakes from 355 mm to 380 mm you will need new rotors, calipers, caliper brackets, splash shields and pads.
That should be it and everything should bolt straight up with no problems, but I'm fairly sure no-one has tried to do it yet. It is possible that the mounting holes on the larger caliper holders/brackets don't line up with the existing mounting holes in the hubs but I would be surprised if that was the case.