Well, in the tele-tubby-world of TW, where no player can lose anything and gaining is everywhere, we also see a ladder which works this way!

It counts wins (no matter who you play) - You gain the same points, if you beat lvl 1 player or if you beat lvl 10
Which is more than stupid!

It let you play siege and sea-battles, even you never selected it.

People see your lvl and just esc in the setup screen.

How it should work.

The points you gain should be determined by the lvl of enemy you play!
You shouldnt gain much points (or maybe no at all) by playing lvl 1 player as lvl 10 player.
The bigger the difference, the lower your gained points should be.
While it should be different for the other people, if you beat a higher lvl than your are, you should gain a lot more.

Now this system isnt really good as well, since everyone gain XP, even while losing, people will end with high lvl anyway.
So this would be my favorit:

The XP you gain (we had a similiar system in STW, which was very very good) should be determined by the current standing of your enemy in the ladder. So lvl wont really matter, what matter is the current "ladder-XP" of the player/team you meet.
If you play a player/team who/which is top10 you should gain more points than playing someone who is Nr. 1000 or 2000.

As it is right now, people who playing a lot, especially at times, where the top teams wont play, can easily rank a lot higher, than teams who play in the peak, where they fight other good teams more. Playing much shouldnt have any effect at all, only skill should count!