Even if you change just the speakers (by just the speakers i mean no amp no new wiring only replacement) the electrical warranty is void.
They logic behind this they gave is: supposs an after market speaker has internal shortage which can result in some electrical shortage of the car wiring that will put the speaker at fault.
So leave alone the fact you can alter the wiring of entertainment system even if its grip to grip but still the camera wire will be new addition to the car. And also apply the same internal shortage of the device formula.
Its far better to spend another 30k on the original navi and lets assume the aftermarket navi and all electrical systems work fine and no warranty claim is ever required, your car will be always tagged as نان جینیوین سسٹم والی گاڑی