The really loaded topic would be the technical fact that the proposed “ignore for ADR” checkbox to make mobile gateways safe would also make these non-destructive (doubly so if it were to activate automatically on any gateway that wasn’t reporting uplinks on a variety of channels/SF’s…)
In terms of policy, nodes intended to use them would still abuse one channel/SF (same as they would if used outside of TTN) but at least they’d no longer trap other people’s nodes.
In some regions with multiple uplink channel groups, it would be possible to entirely dodge the issue by agreeing to place the non-compliant devices and nodes on a different sub-band than the concentrator based gateways and nodes.
I fully understand if people don’t want to take those enabling steps; but in a technical sense using one or both is as safe as telling people to go make their own network is.
And absent any of this they have no place on TTN.