Not to pour oil on the flames, but, let's consider this from a factual RAW point of view then.
Firstly, I find it strange that you, Pax, demand that physics need to be obeyed, then stating that RL doesn't have anything to do with the issue at hand. But that's beside the point.
Secondly, and more importantly:
Nowhere in the core rulebook does it say that motorcycles aren't riggable without modifications. In fact, we all know that vehicle rules are woefully underrepresented in the current edition. However, we have one mention of the rigger adaption:
QUOTE (SR4a @ p. 348)
When added to a vehicle, this “black box” allows a character with a control rig (p.338) to rig the vehicle (Rigging and Drones, p.244), either through a direct fiberoptic cable or wireless link.
Note, 'a vehicle' does not preclude or state special requirements for a bike. Armed with this knowledge, I proceed first to the Control Rig cyberware, which again does not mention bikes at all. Look it up, it's on p. 338.
From there, back to p. 244, where the Rigger Adaption so helpfully leads us. Again, nothing about bikes, at all. Nothing much about rigging vehicles, too, but you can jump into a drone, so let's look there.
P. 245, that is.
Again, no mention of different kind of vehicles needing different requirements.
pp. 225-226 is the next stop, it describes VR.
QUOTE (SR4a @ p. 226)
Perceiving the VR Matrix in its full glory overwhelms the physical senses. Any action taken in the physical world while in VR suffers a –6 dice pool penalty.
Emphasis mine.
Now this is some actual information we can work with. It says on the one hand, that the hacker's senses are overwhelmed, and on the other, that any physical action suffers a -6 modifier.
Now we can conclude that it is
a) Not impossible, but rather inconvenient, to rig a bike, according to the rules presented in the core book, on grounds of VCRs netting you a smooth -4 to your vehicle tests, or
b) That you can rig a bike just fine, with the thought that the rigger's senses are overwhelmed, but those are actually being replaced by the vehicle's sensors. Furthermore, he doesn't go limp, since there is no mention of that.
But let's go a bit further and take a look at Arsenal, where the Motorcycle Gyro Stabilization is mentioned, which, btw, was never included in any rigging a bike requirements, ever.
QUOTE (Arsenal @ p. 140)
Thanks to technology, your bike no longer crashes to the ground when you forget to employ the kickstand. With motorcycle gyro stabilization, the bike will stay upright in all but the worst conditions. In cases where a Handling failure may bring about a motorcycle crash, add 2 to the vehicle’s Handling to represent the gyro stabilization’s assistance in keeping the rider upright.
Again, no mention of being a requirement for rigging a bike. At all. It is helpful if you make a crash test, and it is helpful if you want to use the thing as a drone, but neither do you need it for rigging, nor for actually using it as a drone.
For that, you only need the Rigger Adaption, which is again described, with different, expanded wording, on p. 142
QUOTE (Arsenal @ p. 142)
This upgrade installs a basic black box to allow a rigger to control a vehicle and to “jump” into it if required. While this is a common modification, that doesn’t mean that it is any less complicated. A datajack must be installed to allow fiberoptic communication, followed by a Signal 1 wireless system so a rigger can control the vehicle wirelessly from the driver seat, a basic sensor network so a jumped-in rigger can sense the area around the vehicle, and a control system interface to allow the rigger’s black box to control the vehicle. All off-the-shelf drones come already equipped with a rigger adaptation.
Again, there's no special mention of additional systems required for rigging a bike. More importantly, there's the mention of 'a basic sensor network, so a jumped-in rigger can sense the area around the vehicle' (perhaps overriding the overwhelmed VR senses?) and a 'control system interface'. What exact nature this interface is, is left open, but I think you can safely rule this as a system that allows a bike rigger to actually rig his bike without having more problems than without the rig.
Edit: Actually, I found something new to me, while reading up on Hot Sim. You only receive +2 to
Matrix tests. So, the VCR replaces the matrix bonus with a +2 bonus to vehicle tests, instead.