Nah they are definitely going to have to change Full Thrust and Chaos Thrust, Fang and Wheeling are pretty much combo extenders as is.
Like I said, the easiest way for them to do it, is to make the middle part of the combo decide what the finisher and the extender are so as to relieve button bloat.
True Thrust into Disembowel or Vorpal Thrust will then change what the 3rd button is, if you hit Disembowel it'll change to Chaos Thrust, if you hit Vorpal Thrust it will change into Full Thrust. With the 4th button being either Fang or Wheeling based on whether or not you executed Full Thrust or Chaos Thrust. Alleviates at least 2 buttons from Bloat, and keeps controller players from having to switching between rows whenever they execute Fang or Wheeling, this would also mean they don't flow into the other either but sacrifices must be made, especially since it's not like those two abilities extend the dragon eye gauge like they used to back in Stormblood.

Jumping: So what if it does allow you to cheese certain mechanics, you can't cheese them all, if the floor drops away, or becomes an instant death zone oh well you die. Black Mages are expected to learn the timing of entire fights so as to best utilize their leylines, what's to keep dragoons from having to do something similar in order to plan their jumps?

Breath Weapon: Why would it need to be a long on going thing? It need only be an animation of you jumping up and then an arc of fire-spewing forward in a cone. Not asking for Flame thrower for Dragoon.