Just a thought...players have been asking for an ice region for a few years now. Why not have a "cold front" blow in during the winter months and freeze over parts of the map. I can see this adding new game mechanics like having to navigate around icebergs or having to deal with blizzards. The blizzards could act similar to fog and white out the area with a dense snow effect. This would be a cool opportunity to change the layout of popular islands and outposts as well. I know this would be a huge undertaking and probably isn't something that could be added in a short period of time. You could even introduce penguins and other critters into the Sea of Thieves with this change.
Other seasonal event transformations would be great as well. You could have additional spectral activity showing up around the seas during the month of October or something like that.
