Kalista's Q seems like it's on the wrong spartan
but yeah lets just have the original guy have a single target spear that doesn't feel thematic or exciting like it should to just throw spears at dudes

You're missing the point.
More than likely, Panth would have to lose a significant amount of power to get this change, and it probably wouldn't be in a way you would prefer it to be.
Also, long range spear crits wouldn't be allowed.
Despite Pantheon being one of my favorite characters, his design is horrible. Point and click Fighter/Assassin AD Caster that can't decide if he wants to burst, frontline, disengage, engage, peel or close out targets. The only thing that is clear is that his Spear is designed to chip away at the enemy's defenses and then he goes in for the final strike, kinda like a Ranged Xin Zhao. If anything they should do not high damage but be almost constant, kinda like Kalista's Q which is why it upset me.
His Q needs to be a skill-shot. Probably shorter range than most, nowhere near the length of Nid's and probably not close to Kalista's either. The crit is mostly part of his identity but it basically just a different way of giving him an execute mechanic.
You are right in saying that the crit probably won't remain for Spear Shots, but it will still be there in some form or way, at least the execution playstyle and idea.