I think all the discussion so far has missed a fundamental point, that with the system at present even published approaches are merely advisory. The legal position for public transport flights is that the company must include in its ops manual procedures for every airfield they could use. 99% of times this is covered by adding Aerads or Jepps as an appendix to the ops manual, but there are also plenty of examples of "company" procedures for airfields without approaches, or often where the published approaches are for Cat A & B only.
In the past when getting such approaches scrutinised by the CAA for inclusion in an ops manual they have said that they are only too happy to look at anyone's private procedure as they would prefer to encourage safe procedures than have accidents. This was a few years ago, so they would probably either charge a fortune for the service or mutter about liability now...
The interesting legal point is that the approach ban only applies to published approaches!
Obviously this is all unrelated to off the cuff gps approaches, which are foolishly dangerous.