I am not a lawyer but EU Regulation No 1009/2010 on type approval requirements for wheel guards states:

2.1.1. In the part formed by radial planes at an angle of 30° towards the front and 50° towards the rear of the centre of the wheels (see Figure 1), the overall width (q) of the wheel guard shall be at least sufficient to cover the total tyre width (b) taking into account the tyre envelope as well as the extremes of the tyre/wheel combination(s) as specified by the manufacturer. In the case of twin wheels, the tyre envelopes and total width over the two tyres (t) shall be taken into account.

In short: Nothing is allowed to extend beyond the wheel guards. Now, look at the image above again.

Deviating materially from the type approval makes your car not street legal as far as I understand. But this is a matter for a lawyer. Surely there is a reason why these psychopathic car mods are impossible to find in all of the EU on public roads.