Missile Launcher Pantheon
I don't have any art cuz I suck at drawing but here's my concept
Pantheon will look like a missile launcher vehicle with a rocket on his back His hands could be one of those launchers with all the missiles that shoot lots of tiny missiles
Q-Throws a heat seeking missile, this makes sense since his Q is targeted, we can even have a target on the champion he uses Q on like Urgot's E>Q and have the same/similar sound effect
W-Not sure about this but we could hide his missile and have it go down
E-Shoots tons of tiny missiles in front of him from his "hands"
R-Pantheon becomes a Nuclear Missile, when he drops down there is a mushroom cloud effect and waves of radiation going outwards.
Bonus-When Pantheon ult's his team should be able to hear "Nuclear Launch Detected" and if it's canceled you team should hear "Nuclear Launched Aborted"