"Good reason" can be "exploration/survey" for a portion of the unexplored/newly explored part of the cave, or maybe "training" for a surveyed/explored/made safe portion of the cave...
If you divide the cave in sectors, then the "license" can be limited to a particular sector where good reason can be shown/demonstrated, so you can make a section still under exploration off limits other than for the exploration team (for the safety of the exploration team and less experienced divers), while another sector ("easier" and without exploratory lines...) "open" to all those with any cave C-cards.
"Good reason" = "Common Sense"
It is not a "nanny state" and has nothing to do with state laws or regulation.
It is purely a private sector expression/form of self-regulation/organization to responsibly increase cave diving safety and protect the caves and the environment (which will also protect the business which has developed around cave diving).
You are already digging yourself deeper than that uncommon "common sense" would make.
First, someone has to define what is common sense - the least common of all sense.
Then define what good reasons are common sense.
Then what is the limits to responsibly increase cave diving safety . . .
Then what will do all those things and protect the business(es) . . .
Yes, you are indeed defining a nanny state.