Is there anything in this game exept PvP?
Yes, a bit.
But what balance there? You don't want BGers/EWers to use laser rifle and flamer from beggining to kill cents?
About what you said that low lvl characters using BAs to kill strong mobs, hahaha, let them do it if they want, there's nothing bad in it, if only they hunting in some dead place where are no players, because if someone enter encounter and see 40 HP guy in BA he will be happy that such low levels are avaible to use such armor.
So your suggestion is: low levels are using 10mm pistols and leather jackets to kill mobs, then they are raising to 21st level and again can use all? If they are equiping BA on 1st level, there's voice in his head tells him "You're too weak for this, noob" and removes armor from him. How it can make your gameplay better? You'll find it entertaining? You won't leave FOnline if only you'll be unable to use BAs and laser rifles on 1st level? But stay in game if you'll see every low level running with 10mm pistol and jacket?
Classes? There're already classes, characters are limited, if you're sneaker, you're sneaker and nothing else, if you're burster, you're burster and nothing else, if you're thief alt, you're thief alt and can't do anything, if you're lockpicker, you may only lockpick, if you're sniper you can do only aimed shots, if you're crafter you may only craft, if you're crafter with combat skills then you again can only craft.