It was supposed to introduce its own ranking system, however i think this got scrapped with patch 1.3, additionally PoE wont allow you to increase your BF2 rank.
Everyone in the game is a private which to be honest is a good thing as points, ranks, medals are irrelevant now, everyone is playing the game for FUN!
PoE wont have any impact on BF2 Vanilla, its just a mod you can switch between BF2 and PoE, just as the same you can switch between BF2 and BF2 SF.
A couple more mods to keep your eyes out for and these 2 are the big ones, Forgotten Hope 2 and Desert Conflict.
http://forgottenhope.bf1942files.com/index.php?flash=yeshttp://www.desert-conflict.org/First Strike (star wars mod) looks interesting.
http://www.doomlab.com/bf2topmods/