It should become normal practice during precautionary landings to actually land
That's very interesting... and I can see the sense in what you're saying. But I don't know that I agree.
When I did my float-plane rating, I did actually land off of PFLs. Of course there's not much difference between a planned landing on an unprepared lake (which is what I did for most of the rest of the rating) and an unplanned landing on an unprepared lake, apart from the lack of power. Did I benefit from it? Well, not really.... there was certainly nothing lost by landing off of PFLs, but I don't think there was very much gained, either. The landing itself is no different to a planned glide-approach. And it's perfectly possible to see if you're going to make the field (or lake) without actually having to land, and to make appropriate corrections to your technique for next time.
As for doing the same on land - in a field, there are all kinds of invisible obstacles that may be lurking in the vegetation, waiting to cause damage to the aircraft - something which isn't going to happen at an airfield. I know you stressed that it would be done under controlled conditions.... but how? If you're going to pick a specific field that's been prepared in advance, it's no different to doing a glide-approach to an airfield. Part of the skill is in picking a suitable field, and that means having a number of fields to choose between - not all of which will be suitably prepared.
FFF
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