Better air defence is not a guarantor Against missile storms, they can come in hundreds in time of war and will overwhelm your defences, so for that you need an equivalent deterrent both in quality and numbers..
As for Usrael, there won't be any better ties as long as there is no Palestinian state beside Usrael.. KSA and Usrael might have a common foe.. but both work with the US each on its side defending their own interest but not together.. since they do not share interests..
As far as ICBMs, nukes...etc are concerned, Egypt most probably have gotten the technologies and blueprints of everything that North Korea has tested successfully.. including ICBMs and miniaturised nuclear warheads for hydrogen bombs..And most likely the full nuclear cycle technology..
Just remember that it is Egypt who has provided the first BM (Scud missiles) to Nk and above that helped with financing, developing, providing new technologies and testing.. the other fact is that Egypt (under US pressure for decades) cut its diplomatic ties with NK only after everything was tested and proved to be viable.. So no worries there..