Thanks. I've now taken a look at video which shows wiring for European LED lights so I've now got a sense of how to remove panels in rear without breaking anything. They removed rubber conduit on one side, but I agree should be possible to snake wire through (without perforating rubber tube) without actually removing conduit. I imagine that it would be a bitch if clips broke as water would then leak in necessitating replacement of conduit necessitating disconnection of wires in hatch for lights and heated glass necessitating removal of connectors to get wires through conduit and reattaching connectors assuming you have not messed up the pins, blah, blah, blah. Clearly it would be best to keep disassembly to minimum especially given cost of VW replacement parts.
On wiring front, I'm not a fan of running wires behind weather stripping due to potential for abrasion resulting from repeated door closings and door movement over time and I'd rather stay away from air bags if possible. As to connecting load to overhead console wiring, I would think that from electrical perspective this is really equivalent to running load off interior fuse box as the power leads in console are already off of a fused connection (it's not like running a heavy amplifier load directly off battery using separate fused connection, for example). I would also think that the light electrical load of a dash cam will not create any voltage spikes in circuit beyond that created by turning overhead lights on and off creating any havoc with electronic modules elsewhere in car. Finally, I suspect that overhead console lights are grounded to body of car at console area (and not through separate ground wire) so opening up console area allows grounding of dash cam circuit is same area which I think is also good.
Finally, dash cam uses a USB connection for power, i.e, a 5v lead, so you are right about going from 12v to 5v (this is also an issue when using a tap-a-fuse). Speaking of which, tap-a-fuse product is not so good when you need to change fuse in same area. I used one once -- never again.
This is the first car I've owned without a factory service manual or factory service electronic files which is already proving to be a giant PITA.