nehunter, I'm not a professional dock designer, and I really don't know what dock design would work for your specific situation. I would still strongly recommend consulting a professional dock designer/engineer to determine the best approach.
However, I included a bit of information about my floating dock, just in case it might give you a few ideas to think about.
This is a 'stiff-arm' floating dock that I built to handle about a ten-foot change in water level, although it generally only sees about a six-foot tidal range. This is located in a tidal zone, but it's in fresh water, since the salt water from the Atlantic doesn't make it this far inland. Okay, it's not on a pond (unless you consider the Atlantic to be a very large 'pond'), but I thought it might be of some interest here.
I ordered the aluminum gangway from a company in Maine, but otherwise I constructed most of the components myself.
It has a pair of stiff-arms (or 'struts') that are almost 29' long and a 30' aluminum gangway that is hinged at the shore end but has rollers at the dock end that allow it to roll back and forth on top of the dock. The stiff arms are cross-braced with hefty wire rope (steel cable) in an 'X' pattern in the plane of the stiff arms. The anchor posts on the bank are removable, since the entire dock has to be pulled out each year before winter or else the river ice would destroy it. The bank is solid bedrock, which makes for a firm anchor system. I fabricated the brackets on the top of the anchor posts on the bank to match the attachment brackets on the floating dock corners. The side of the dock where the stiff arms connect has extra float drums under it to make up for the extra weight of the stiff arms and gangway and keep the dock level. The floating dock itself is fairly small (only 6' x 20'), but of very heavy construction, and the extra mass and low freeboard add to its stability in certain respects. Keep in mind that the greater the change in water level, the longer the gangway and stiff arms would have to be. There are a lot of other design and construction details that I could add, but they might be better addressed in a separate thread. Suffice it to say that I came up with a few little details that I haven't personally seen on other docks, and so far, it's working very well. Again, this system might not necessarily work for your application, but I hope the information is useful somehow.
NOTE: The small vertical pipes on my floating dock do NOT extend down to the river bottom. They are not pilings. Their only purpose is for mounting a ring buoy and a future barbecue on the dock.
Stiff-arm dock:
Wire rope (steel cable) cross-bracing:
