For what it's worth, however, hunt test are extremely resource-intensive to put on. In addition to finding and reserving and probably renting vast tracts of suitable land, the small size of many host clubs combined with the huge amount of manpower required means workers need to be hired for many tests. Birds, wingers (and backups), vehicles, guns & appropriate ammo, permits, etc. in addition to normal all-venue costs like bringing in judges from the far corners of the earth, etc. For tests with live fliers, they need birds for every single dog entered...no reuse.
There are reasons that entry fees are $65-100/entry. Even then it's tough for a lot of the clubs, despite big entries. They are already full-day and multi-day events (a single Master test usually takes 2 full days to run). The small groups of diehards who put these on have many motivations, but at the heart of it is preserving traditional natural instinct in gundogs. Considering the current breed system disallows bringing in outside bloodlines by merit, expecting them to take on additional effort and expense for dog who cannot contribute to the genetic perpetuation of gundogs as a type would likely be a problem.
In addition, a line should be drawn between hunt tests and field trials. Hunt tests are to test the dogs' instincts against a standard, primarily to evaluate potential breeding stock and verify natural ability, at least at the lower levels. Field trials are judging relative to competitors, with dogs downselected at each stage of the test until only a few top dogs remain at the end. I would personally be somewhat more open to allowing all breeds in the field trials vs. the hunt tests simply because FTs are already so artificial and it would just mean a harsher downselection. And it's already mostly FT-bred Labs whose suitability as a natural family 'triever can already be called into serious question...
I'd have to think on it some more, but just to give a little background.