This is a really great thought/proposal, Niall. One does have to think out of the box from time to time, and this is a good time for this issue. Once you think about this issue (which you have inspired at least me to do) you wonder why bunekrs are treated any differently than any other part of the course through the green. I'm sure Tom is right when he talks about the fears of the powers that be regarding "improvement" of lies, but is there really any basis for those fears, particulalry for those elite players who are under more and more constant scrutiny from officals and armchair rules officals? Frankly, as a players for more that 50 years I can imagine how I might improve a lie through the green but not in a bunker (e.g. "ground" the club aggressively behind the ball) but I do not have a clue as to how I might do so in a bunker, even if I were to join the dark sides of rules cheats and casual golfers. All I can even think of is getting some sort of information on the state of the sand, but I can get most of that already within the rules through the act of taking a stance. As long as it is clear that grounding must be done done gently, nay even delicately, this change in the rules could be done. And, while we're at it, why not make a similar rules change for water hazards (yellow or red)?
Cheers
Rich