as mariner pointed out we should have something to chase for if we should continue playing, so some kind of "pick your own toon"sould should be a nobrainer to create longterm motivation.the sad truth is, we won't ever have a full roster, since there will always be new toons/special toons and crap which will destroy this plan. so give us at least the illusion, that we can complete it one day, i'd say....
i like the way you can get the liliths, you can buy them for FC, farm fragments from time to time or pray to get lucky on special souls