Normally, the top bar icons go, from right to left: site switch, help/review, achievements, inbox, profile (+ mod).
But for a few weeks a year, they go: site switch, Winter Bash, help/review, achievements, inbox, profile (+ mod). In bold: the positions that have changed meaning.
Please leave everything in place during Winter Bash and put the Winter Bash icon at the end, i.e. at the left of all the others. Or put it at the left of the search box.
In addition to the reasons given in the question, the snowflake takes a second or two to show up sometimes, so we see the usual layout and then everything shifting over to make room for the snowflake. The animation can be a little distracting and is, I assume, unintended.
To avoid animation effects, it'd be best to put the snowflake in what is currently unused space in the top bar, so it can just wink in when it loads. The rendering delay isn't new; last year the snowflake sometimes tarried, but its arrival didn't affect anything else. Using that space between the search bar and the gravatar -- the leftover space between layout that starts at the left side and layout that starts at the right side -- should accomplish this.
(I don't know what happens if the window is too narrow to hold everything, but whatever we do the rest of the year should work with the addition of the snowflake.)
