What if broken vessel were in aether:
He would have 2 high jumps and no additional movement options.
When designing broken vessel, beside using only his boss battle moves, i also decided to use the fact that he isn't, himself. But an infected being by parasite. So his movements will be unsettlings and disturbing, while also mimicing other characters from hollow knight with the infection effect on them. Also, when broken vessel will use attacks involving his head, some spores may flinch off and will try to latch themselves into foes. Slowly draining thier life for short time, Like an actual parasite.

*the A attacks*

Jab: broken vessel jab will be one tentacle hit, then his nail, and then headbutt. But if you keep the button pressed, instead the horn dealing damage, the small infection on his head will do small flinching damage before broken vessel raise his head for the final hit, launching foes.
For Dash attack, he will dash forward with his horn at the lead before landing down. Will be great to catch foes unguarded, but will have end lag as broken vessel needs to stand up.
For Side tilt, broken vessel will swing his nail from up to low.
For Up tilt, his infected head will blabber, dealing small flinching damage before they calm down, sending caught foes upward.
For Down tilt, (by the eay when broken vessel is crouching, he'll appear just like when he is defeated so the infection retreat in his head) he will raise his hand and head in manner of "help me" just to hurt foes with his horn
For broken vessel's Side strong, he'll slash 3 times in the exact same manner as hollow knight's first attack. After all, they both have the infection inside them so it does make sense how some attacks will resemble hollow knight as well.
For up strong, broken vessel will violently swing his nail from side to side, like in his boss battle.
For Down strong, the infection will jump from broken vessel's head into both sides of his body, dealing racking damage before jumping back in. But in that spot, broken vessel is vulrnable where the infection were. If you manage to hit the open skull area, it will deal great damage to broken vessel (incase you can dodge before the infection return)
Netrual airl: broken vessel will explode, like the first enemy (infected form). Dealing major damage to foes around himself, and taking a good damage upon himself.
Forward air,, he'll use in up to low nail slash that can spike if hit the sweet spot,
Back arial will be tossing infection from behind in parabola manner (like jumper infected version)
Up air will be another headbutt that can deal good damage if the horn is hitting instead,
And for Down air, just like the infected grubs, broken vessel will release a large orange blob that hit foes in contact. It won't be able to spike them.

*specials*

Netrual special: he will spawn one of the orange blobs that assist him. They will deal below averge flinching damage and will aleays fly to the nearest opponent.
Side special: he will take a second to charge, and then will automatically dash forward with a massive nail slash afterward like in his boss fight. (We can refer it like the dash slash matarial art as well)
Up special: he will be levitating in the same manner as the hollow knight flew up. He will go to a safe distant before going into a free fall.
Down special: as long as the down held, he will shake his head violently, releasing small orange bubbles to fly upward. However, after a few seconds of doing so, broken vessel will need to charge that abillity and won't be able to use it after a while (otherwise it is super broken)
If he uses down smash while on air, he will instead drop down and will only release 2 blobs one each side and will need half of the time for his cooldown.

*Final smash*

For broken vessel's, final smash, he will use the help of the one controlling him: the radiance. After using the special, the blob will jump off broken vessel and he will lie on the stage, invincible to any incoming damage as well as unable to move. The infection jump to the back of the stage, revealing itself to be the radiance. The radiance will then emit light rays from left to right. It is shieldable and is dodgable, but being hitted by it dealing A LOT of damage and knock back. After the entire stage were covered in light, the radiance flys up and the infection return to broken vessel.

*the other stuff*

For colors, we will use the higher beings of hollow knight. we can all change the infection colors and a bit of broken vessel's capes. First we have the orange infection with the night cape, then we have red infecfion, his skull will have the design of grimm with grimm's cape, resembling the nightmart heart, then we have blue infection with blue cape, resemble the lifeblood cocoon, then we have green infection with green cape, as resemble to greenpath and unn, then we have black infection with black cape, resembling the entity lord, then we have white infection and silver cape, resemble the king, then we have golden infection with his face replaced with golden skull and golden cape, like the godseeker, and lastly, we will have zote infection with grey prince zote cape, his special will be zotelings and final smash will be grey prince zote.
For stage intro, the body will be lying as the infection gather up, only for the vessel to stand up and scream. For taunts, the first one can be the vessel looks up, like after he does so after he takes certian amount of damage, the second can be him stab himself like the hollow knight trying to fight it (but he won't take actual damage from it. Some foes may if they stand behind him) and his last one can be another scream.
And that is my idea for broken vessel moveset. I just wanted to share my ideas, hope you like it!