I'm not equipment savvy, other than my small tiller for gardening. I did own a skid steer/mini dozer, but didn't use it to destump. My experience when I cleared a much smaller area, is that those small saplings/trees rot out quickly. So certainly within two years, those should have significantly decomposed, especially soft wood like pine, when you have nice moist soil. If you could plant in the less stump burdened areas and let the small stumps rot out over the next year or two, that will actually add to the soil as well. Of course, it does sound like you're trying to immediately put the plots to work.
On a side note, for bigger stumps - primarily small maples to thin his mini 50ac forest (and none pine... but maybe it would work), I had a neighbor who inoculated those old stumps with mushroom plugs. The mushrooms really quickened the decomposition and he got free edibles. You could innoculate with any mushroom (even unknown wild and possibly poisonous) if you aren't looking to harvest as well. Not sure that would work well for fully cleared areas since mushrooms tend to be in darker forested areas, but just a though.