Being in the excavating business I have cleaned out a few ponds over the years, the the easiest way, if you have room behind it to accommodate it is to cut the dam and push the really slimy muck out through the cut, then repair the dam, which is not a problem in the least if done properly but definitely has to be done correctly, in several cases we were not able to do that because of property line restrictions, in which case we had to let the water out slower, and still cut the dam so it stays empty for a summer or two, that old muck gets just stiff enough where you can bucket it out and carry it up away from the property line. cleaned one out behind an old barn lot that had 5' of muck in it, that took a couple years to get stiff enough to carry in a loader bucket.
I agree, a pump in a 2A pond is like a fart in a hurricane, better have a lot of time on your hands.

All the really good ideas I've ever had came to me while I was milking a cow.