I do many RTMM excursions at Alaska Adventures VA. (
http://flyaka.com/) if you want to look around. Many of the SAK/Tongass coastal cabins are water moorings but there are a few cabins or other type locations in the interiors but only a few have small strips for access and they're definitely not an easy land.
Most cabins around PF20 and westward towards the ocean and being salt water: the water moorings don't actually freeze over during winter. Water is almost at ice temps but still liquid!. Cabin Heat, Carb Heat, Pitot heat are a requirement in this winter flying season!
(Our last float trip of the year is currently active. It is an excursion in RTMM territory (PAKT and PF20/21 and @100 nm radius to some very interesting locations. It runs until Dec 21). In mid January, will bring out excursions into the RTMM CIRP (Ice Fields) which truly are winter adventures: landing on ice fields and glaciers with Tundra wheels or ski/wheels).
Now, there are many charter companies out there in several areas. I think you'll find that Juneau area closes End of October and resumes in May. Just do a quick search and you'll get a feel for the areas and their operations.
Norm