This is what they do on wow, once so much of the playing populace has 'earned' they new gear they effectively give it away to let new players catch up easier since there's already a skill/knowledge gap. Better players having better weapons doesn't help new people get into the game so this probably keeps more people playing
Yes, except that the unlock weapons are not better or worse than the originals in many cases. Valve took special care to make the new weapons DIFFERENT, not outright better... With exception to the medic items "Ubersaw" and "Blutsauger", but honestly, those arent overwhelming advantages that kill new player morale.
You cannot stop this, no matter what solution they put forward. Do a server search for "achievements_idle" and marvel at how many people are cramming themselves into these servers to farm unlocks.
Since you're familiar with WoW, I'll just say that they've successfully ported the FUN and EXCITEMENT of Alterac Valley into team fortress 2. Now you have a bunch of cloaked, macroing idiots standing on top of ammo cabinets on live servers instead of class inflation. Not a very good FIX, is it?
Item trading is equally pointless. I dont want to "EARN" crap, I don't want to "TRADE" with people, I just want to play a damn FPS. Keep this MMORPG crap out of the FPS genre. Just give everyone the ability to customize their loadout and just run with that. People should play for fun, not for unlocks.