The first question is why change, and there is an option suggesting keeping the rule as is.
The objective stated is to align with IACO, or perhaps JAA rules. We have seen in the case of the NPPL the usefulness of having national flexibility to suit local conditions.
Another objective is to make the rule more readable, and the question is then does the proposal achieve any substantial improvement.
In the discussion document/proposals para 4.4 is written as a blank cheque, intentionally or otherwise.
The proposal reads as if it is helicopters which are driving the changes, so it is for those experienced in their operation to come up with rules suitable for their type of flying. This will not necessarily translate to be suitable for light fixed wing craft.
A hugely important question for the GA fraternity is, will any rewrite of the rules make it more certain that pilots incorrectly accused of infringements will be aquitted.
As to any safety consideration, the question to be asked is how many accidents have occoured while keeping to the current rules.
Flight under the London TMA, and into airfields in this area already requires particular care, will any of the proposed changes make this safer or worse.
It is my opinion that the present 500 ft rule gives much more flexibility than the proposed, is understood by all pilots, and any change may well introduce problems, some of which have been discussed in this forum.
Having made the above comments I would like to read more opinions before submitting comment to the CAA.