If you can play alone with 2 or more characters, then you'll depend less on other players. Makes game a bit better in some way if you ask me. All the Russian servers allow multi-loging and they have high population. This is not forcing people to play 2, 3 or 4 characters, you can still play on only 1.
Either way I find this to be the problem of the game itself, not the system which is used. Look, if you allow multi-log, those who want to win badly will make lots of pvp characters and use them all in fights, swarm with mults, and people will have mults working on crafting, making gain of items, ammo, armors, weapons, easy. This will encourage people to keep leveling up characters in order to win in large battles with more mults than the enemy.
If you do not allow multi-log, people will use it again, they will cheat and those who are not afraid of cheating will use mults for crafting and in fights.
This cannot disappear, because of having multiple characters gives huge advantage to the game, because in game items, resources are gained faster with multiple characters and fights are won easier with larger group of players. Even if your group get's wiped out but you damage the enemy. When you can jump back on them with an army of secondary mults you will win the battle. Town control, gang battles in this game are based on number of characters not to mention npc mercenaries. Now don't go saying that some might have better skill than others. Of course that people on voice chat and experienced in battles has larger chance of wining. But swarm is a swarm... If devs return the old game mechanics, drugs and other things. A group of people could prevail over others in terms of fighting. As long as they know the secrets which others don't. But once all are equal, only numbers count.
I won't say this is an idea or suggestion. But imo, removing the capitalistic way of crafting and trading, wasting time on this; and instead allowing people to gain items as rewards for something done in the game, or allowing certain players to levelup to higher level than others, also as a certain reward, it will un-balance the game a bit, but will remove the desire for dual loging, when you only need to focus on one character, instead of massing them for purpose of swarm and crafting.
Think about it...
Also I want to add on the PvE side, the game has no Boss or anything similar to it. Theres no Franky to win in a fight, no king rat or some deathclaw king or anything. The only things people can fight against are same old lame boring creatures that appear, and npc caravans and patrols. The final option which most take are other players, gangs and all the rage there is to it
Adding an route in the game where you do more PvE than PvP will make this more look like a game. Otherwise it's full PvP and people shouldn't whine about being pked or playing anti-pk. Makes no sense. Well it does, this game makes sense for people living on ingame items, which are greedy people, thieves and craftoholics. The only remaining people playing the game are those. That's what guides them trough the game. Craft, greed, kill & loot. My gauss, my collection of BA's. Me happy. Is a good game. Fuck this...