.More Characters such as Danzo, Raikage etc.
.Peinis to be in UNS3.
.A fix for the KNJ system - i.e. limit per match, or the an increase for the amount of chakra required etc.
.More u1's per character.
.Better u2's, like in UNS1.
.A more difficult online ranking system, mabye more ranks, more unlocks etc. It was too easy in UNS2.
.Punishment system implemented on those who D/C, i.e. if some-one D/Cs too much/frequently they start to receive some sort of punishment [e.g. BP loss/a loss added on etc.], I personally think just giving the person who D/Cs a loss is enough tbh, however some people have bad connections and sometimes "time-out"/DC by accident, so it has to be fair to them.
.The option to play campaign in 2 modes/options- 1 being the adventure mode type like an RPG in UNS2, the other to simply play all the story battles and events/cutscenes etc. so you don't have to do all the f$%^ing running around if you don't want to. xD
.Everything else regarding UNS2 is generally fine.