I am reasonably sure doughnut shops, especially the more popular chains, use some sort of plant oil in their fryers, so I wonder if one could raise the general level of health among the populace by switching to good old saturated fat for the frying and a non-gluten flour for the dough. And for the icing, well we could avoid the much maligned high fructose corn syrup. Obviously, those choosing to eat these 'improved' doughnuts would still get a ridiculous insulin rush, a lot of sugar, and not be anywhere near as healthy as the people who just generally avoid doughnuts.
I suspect they'd be healthier than they would have been had they eaten the doughnuts currently churned out. Conventional low carb thinking would suggest a marginal change like this wouldn't help at all because the insulin reaction is in itself very damaging, but perhaps, in the absence of a perfect choice, shutting down these two other damaging pathways would improve things considerably- possibly while keeping all the tasty hallmarks of a doughnut intact so that one could successfully compete!
Of course, one couldn't advertise, in this crazy lawsuit culture, that we actually though our doughnuts were less damaging to consumers than other doughnuts.