I agree with ITD on all points, Nero. Perhaps "Just Sold" could comment on the effect a breakwater would have on a neighbor's property, but I doubt it would have any effect. Unless you need an "abutter waiver" from that neighbor to install a breakwater (or a new dock, for that matter) closer to your mutual property line than is allowed under the reg. (20' I believe), I wouldn't think their appeal would prevail. (I'm not a lawyer, however!
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If the cost of a breakwater would be more than you want to spend, I'd at least go with a permanent dock. In a windy location with a 4,000 lb boat, I would feel much more confident knowing I had my boat secured to a permanent dock, especially since you indicated you could be away for extended periods. A well-built permanent dock requires fairly little upkeep. We had our dock built 11 years ago and it's in excellent condition with virtually no upkeep other than an annual checking of the nuts and bolts that hold the dock posts to the outside stringers.
We run an ice-eater in the winter. It's on both a thermostat and a timer, so 1) it only runs when the air temp. is below freezing and 2) it only runs during the hours I set the timer for. We figure the ice-eater adds about $50 to our electrical bill in each of Jan. and Feb, and maybe $25 in Mar. The ice-eater provides sufficient open water to allow the ice to expand and contract, and rise and fall, without damaging the dock. In our 11 years here we only had ice damage once, three years ago when the ice started moving around while it was still about 12" thick and a north wind blew a large section of it in against the end of the dock. That pushed the two end pilings in a bit, but the repair was not expensive.