I mapped my 4 player control panel defaults as P4 - P1 - P2 - P3, because that makes all the 2 and 3 player games in the correct orientation and all I had to do was remap the 4 player games.
That makes sense for 2P and 3P games.

I've never understood putting Player 3 all the way on the left. Can anyone explain the rationale of that to me, because it seems to get repeated a lot?
I think the reasoning process went something like this.
1. First group: P1 and P2 get the middle positions because most games are two player.
2. Second group: P3 and P4 get the outer positions because less games are three or four player.
3. Order within each group: Player numbers are arranged in increasing order from left to right.
Applying those three rules, you end up with this pattern.
First group
- P1 center-left
- P2 center-right
Second group
- P3 outer-left
- P4 outer-right
Scott