My search for dragline advice almost exactly matched your experience!

One of the recurring posts on Pond Boss is old ponds that have filled in with muck over the decades. They are very difficult to clean out, even with the capabilities of modern excavators.

I think a good operator on an aged dragline could clean out those old ponds with greater efficiency than just about any other method.

If you are forced to put some significant money into your dragline for repairs, then maybe you could make it back by getting a little work on your neighbor's ponds. (Especially since you will be an "experienced" operator after excavating your own pond!)