Niall,
You are correct that the triple green at Blue Heron works because of the short approach shots.
I am not sure adding yardage to your driveable par four would be an answer to a safer solution regarding a possible triple green, though. Depending on the distance of the hole, I am guessing that most shots are bouncing into the green at that point as opposed to a full iron of any sort at a certain trajectory. The drives into the hole are low and would do less damage, if that makes sense. A big concern about items like this is the safety liability, which is why I said a bouncing ball from 300 yards or so would be pretty tame if off-line, more of a nuisance than a danger.
The second shot, for the most part, sounds like it could be just a chip or a bump and run, therefore, I think that adding yardage wouldn't help at all and, like you said, not be as much fun. How long is the hole you are talking about?