The thing is that the problem isn't a gameplay-related one,but a thematical one.
I mean don't get me wrong,you are right in that they could make Akalis gameplay unique and better without adding magical abilities to her,but the actual problem is that Riot wants every champion to provide a unique fantasy.
For example when Azir came out,they said that Azir isn't just a sand mage,but he is THE sand mage of the game(other champs with sand powers might come in the future,but none will be mages who specialize in sand manipulation).
However they have also said that they didn't focus that much on this aspect of the champion designs in the early days of the game and I think akali is one of the champions(if not THE champion) where this is the most appearant.
Because the way it currently is,Akali is simply THE kunoichi,which basically means "she is the ninja with boobs",which doesn't seem like such a special theme.