Zero's gameplay will be completely redone in 1.3. He will be permanently holding the Z-Saber like he does in X7 or X8
It will look something like this:
As stable as his current iteration is, it needs a complete overhaul to feel in line like how he would play in a game with proper 3D graphics. I have not decided yet as to whether make him attack while moving or not, but I will make it so that he has a dash attack also like in X7 or X8. He has no proper dash attack for now mainly because it was a reference to the Saber Dash Cancel from the PSX games but it's also time to move past that.
(This is also why Layer won't be in 1.2.x despite her model being finished earlier than some of the releases in 1.2.x)
As for Third Armor X, his vertical dash height is low for the same reason Zero's double jump height is low: Balance.
Falcon Armor X (coming in 1.2.15) will also have a relatively short flight duration compared to what you'd get in X5 or X Dive.
Things will change in 1.3 where most characters will have more movement quirks to them. Thus boosting vertical ascent values.