He's pretty ordinary but I don't think there's anything wrong with being ordinary at pretty much everything if it means you don't really have outstanding weaknesses and he's also young enough to have room to grow and it's easy to forget his experience is from Egypt/Switzerland so he should naturally improve in the PL.
I have a feeling if he was getting the starts he could evolve into a very good player but I don't know if he'll ever get the chance. I think if we ever need to rely on him in a crisis though he'll be reliable for us.
We have enough midfield bodies now. The only change to our midfield will be Cazorla's age catching up with him and in that scenario Wenger has a call to make. I think Xhaka will turn into the king of our midfield in the same kind of way Fabregas did, so at the end of the day it's going to be which player is most suited to playing with him and with some improvement I think Elneny could be that guy in a similar fashion to how Flamini just felt like a perfect fit for Fabregas.