Aircoin can only be alongterm coin if the model can work as the pool grows.
I think it is questionable they will be able to continue to benefit from market inefficiencies to anywhere near the same extent as the pool grows.
So that will mean they will be some kind of Index fund, IIUC, holding a basket of crypto coins. However they still have to pay expenses out of the pool too.
There is no clear plan released how this is achievable, and to get serious investors on board, I think they'd need to explain just how it will work a bit more thoroughly