If i understand you correctly, there are two different aproaches to dog tags.
In my view, dog tag is kind if reward item you can get from PvP actions (TC, New Reno, future possible domination mode,..). Its purpose is not directly related to original holder of dog tag (because he would not have dog tag in his inventory until he would die), but it is related to enemy player that could loot that dog tag from death corpse inventory and collect those.
Motivation is simple... collect as many from enemy, as you can, collect from as many enemies player sog tags, as you can. It supercedes missing statistics (kill/death ratio,...) by in game quasi realistic feature. It could enrich Fonline about new trade element, if you want to create collection of every known real player enemies (forget about boring New Vegas boring caravan cards trading..).
Your idea (Wipe) is that dog tag is kind of reward in NPC factions, if you loose it you could obtain it again (by overcome some obstacle => nobody will wear it), in general (as you wrote it), it is kind of useless crap item after all.
Well, i hope idea with more player vs. player elements would be implemented.
P.S.:
LvL 21 condition i suggested is to dont abuse this feature to kill every bluesuit you will meet.
It is "easy" (i remember that for some gangs in was not so easy) to kill someone, but it is not easy to loot dog tag and collect them from enemies. And of course, if you have many dog tags from one player, it means = shame for that player and possibility to trade them among other players.
Reason is to try new feature, that could work or not. As scypior wrote, it is very simple to be scripted.