As I have learned when you want to emphasis an element that's not the subject you put it in the first position, then put the object right after the verb. Normally it's the adverbial phrase which is mostly about place, location and time. However, must the subject come right after the verb? Here's the sentence I saw:
2003 hatten in der Schweiz ca. 42000 Skifahrer einen Unfall.
The subject is ca. 42000 Skifahrer but it doesn't come right after hatten but the adverbial phrase in der Schweiz.
Yes, it's perfectly fine if the subject isn't in first or third position. The only fixed rule is V2 (verb in 2nd position).
And in theory you can scramble the other parts as you like - putting those with an emphasis to the front. Note that in your quote it's actually two pieces of information that get an emphasis: Time and place. But as you must follow V2, only one can take the first position, the other follows right after.
Semantically,
2003 hatten in der Schweiz ca. 42000 Skifahrer einen Unfall.
and
In der Schweiz hatten 2003 ca. 42000 Skifahrer einen Unfall.
are very similar.
Just for fun, you could stuff the sentence with more information before the subject:
2003 hatten laut Tourismusverein in der Schweiz ca. 42000 Skifahrer einen Unfall.
-> And all six permutations of [2003], [in der Schweiz], [laut Tourismusverein] would result in a valid and idiomatic sentence as long as [hatten] remains in second position.
There is no reason for the subject to come right after the verb. Indeed
(1) 2003 hatten in der Schweiz ca. 42000 Skifahrer einen Unfall.
and
(2) 2003 hatten ca. 42000 Skifahrer in der Schweiz einen Unfall.
are both grammatically correct. The first actually reads better. The reason for that is that we often put the interesting or new information after the parts that set the stage for it. If you think of the sentence as an answer to:
Wie war es 2003? Wie viele Skifahrer hatten in diesem Jahr einen Unfall in der Schweiz?
Then the first version is a natural word order for an answer. The second version seems more like an answer to
Was ist Skifahrern in diesem Jahr passiert?
which is probably less how it was meant. This is a rather slight difference, though.
