Phil I will not go into a in-depth explanation ( I have a brain injury and my grammar is no longer good enough), unfortunately modern vehicle electrical system are not that simple the CAN-Bus (Controlled Area Network Bus) is a communication system that allows various electrical components in a modern vehicle to share data, is does not carry the electrical loads.
As regards uprated bulbs (a) you are increasing the amperage load on the thinwall 0.5mm2 lighting wiring, 05mm has a load rating over a meter of 11 amps a 55 watt standard bulb is 4.6 amps, uprating to 100 watts is 8.33 amp, outside the manufactures safety margin, you also have take into account the lumens of the standard and uprated bulbs, gone of the days of standard round light, lighting design is a very complicated specialised area.
Unfortunately I have suffered a brain injury and occasionally I get confused and often say the wrong thing.