It is rough to be stuck in noob planes when others aren't. On the other hand it does encourage players to spend some money on the game which helps support dogfight. Those who are bold enough to stick with it and earn their coins will gain some skills in the "school of hard knocks". Some may become discouraged and quit.
I've played some other online games where upgrades are temporary and you have to constantly earn (or purchase) points. It can drive you crazy when you come across a clueless noob who is fully outfitted with the best equipment. It can also discourage you from returning when you know your upgrades have expired. Unfortunately the "buy in players" are often the ones who will relentlessly spawn kill, use the most foul language and have no understanding of team tactics.
In dogfight it seems that most everyone who gets past level 15 is really vested in the game. What if it was made so that you couldn't have full access to the best planes unless you signed in on the forum and found some sort of code in an instructional thread or one about ethics. How about "hiding" one in the user agreement right after the wording about foul or offensive language?
Someone mentioned having the game revenue attached to customizing plane skins. Squad graphics on planes would be awesome. Perhaps zup could sell monthly advertising space on the fronts of some of the buildings. It's not like historical accuracy has been fully maintained in every other way. What if you were able to "buy" an approved building and have it set somewhere on the map? Someone who is a patron of the "jolly Roger" might be willing to pay rent to put the building where Pedrinho has drawn it. No?
Just some food for thought.
BTW, don't forget that you can always support dogfight by buying more coins from time to time (even if you already are a "millionaire")