It isn't really worth running a physical attack on this Xerneas as it seems that you were graced with the fact that your Xerneas was just built for fast special attacking. However if your intentions are to run a physical attacking Xerneas then it would be most optional to just get a new one if this is in your reach of course which I am speculating to be so. It has a nature not beneficial for it's attack stat and very low attack IVs so I wouldn't even say it's worth running Close Combat on it as it has access to a special fighting move which shares the same power but however a lower accuracy, Focus Blast. I wouldn't advice replacing this one as it is quite hard to get a Pokemon with such good IVs and with combined with it's Modest nature it can successfully run a Geomancy set which is in fact very deadly.
However if what you desire is a physical Xerneas then yes, it is recommended that you catch one with the Adamant or Jolly Nature or even Naive, Mild, Hasty, Rash, Lonely,Naughty if it is a mixed sweeper you seek.