This is just like Saving Bob the only difference is that you need to save and escort bob out of a certain map, nevertheless its still like pvp'ing between parties.
And yes this may encourage others to gear up but as we all know its not as easy for others, since they cant donate like others too.
In addition to that...
If the leaders of each party would pick his members then as GM Shino said, leaders will try to get the most geared of that job/class for his/her party. And yes you are saying others can join other parties, but what im thinking about that is that average geared players will be forced to team with each other. And if you were to put a battle between them, who would win? A party full of really geared members or a party full of average geared members? this may explain what GM Shino is trying to say on the phrase "he will get picked up while the others forgotten".