Could you lightly mash a soft fruit and add it to the mash (or steeping grains) like you would with pumpkin or squash? I've read about pectin set if you use too high temps wtih fruits, but that's much higher than what you'd do with grains, I think?
With fruits, the majority of the carbs are already sugar. Putting them in the mash will only create problems for the grain conversion, without any potential of benefits from the fruit addition. Yep, fruit beers tend to be harder to clear naturally because of the pectin, and additional tannins.