Interesting question, selective Viz on NETs could be useful, but I'm not sure it is a placement tool, as the GND routing some consider more important than the other end.
I would agree the Autorouter is best left to deal with Short & Simple nets.
As for "finding the nearest connection point from any component to these zones should be easy", that sounds optimistic, especially on 2 layer PCB.
On those designs, I tend to route GND to guarantee pour connections, and I also shove traces to give maximal-pour areas - that means, invisible ground is not a good idea.
All that said, I took a .kicad_pcb file, and did a simple quick Text Editor global search/replace of
replace with the null net field
and loaded that, just to see what happened.
Voila: It imports fine, minus GND rats connections.
Note that any routed GNDs will now cause DRC errors, as they lack Net-Name Trace-Pad validity.
'You can then import the superset Full NET info anytime, on top of this, to add GND (do not forget ! )
I had a quick scan for possible Python Script support to do this, and I can find only partial support of
GetNet, SetNetCode, GetNetname
but no SetNetName ? I did not test if SetNetCode to 0 on a 2 GND was valid.