Got curious about the shield beam so I looked at all 3 boss fights Galacta Knight has. Also figured I'd try to note what attacks he can take from his boss battles to give him a moveset in Smash
At 0:15 his forward and back dashes could be used for his rolls.
At 0:19 that horizontal slash is basically the first part of MK's ftilt so I could see GK having it on the same move. If not then jab.
At 0:22 that downward stab could be his dair and could be a stall and fall. Pretty sure MK actually has that dair in PM with a diagonal variant too.
At 0:43 I don't know if that move could be put into Smash. Maybe made smaller and it could be his fsmash? Has the vertical range of Palutena's usmash though if left unchanged.
At 0:51 I can see a smaller version of that attack being his nair.
At 1:03 there's his shield beam. Not sure what move that could be made to be. The obvious answer would be a special like neutral b or side b.
At 1:10 another potential fsmash given that it looks like it has the range of Gunner's fsmash. Could be made smaller to be a jab ala Zelda or possibly an ftilt.
At 1:20 I can't really see the enemy spawning making it into his moveset. It's not impossible seeing how Dedede spawns enemies with his side special and Bowser Jr. does the same with his down special but there's no real animation for it and GK goes off screen for it which would obviously have to be changed. Could be a Final Smash but it'd make for a pretty lame one unless it was overdone to basically be Brawl Dedede's Final Smash.
At 1:39 Mach Tornado just like what MK has. Interestingly enough, he only goes downwards and side to side with it which MK does for one of his customs.
At 1:54 there's his horizontal slash again but he does the rest of the move too and there's a beam that runs along the ground a bit. Could still be an ftilt or maybe an fsmash. For the latter, I'm thinking something like Cloud's fsmash but with a smaller weapon and a beam at the end.
At 2:14, basically Shuttle Loop al though it's more horizontal than vertical. Could be a side or up special and it could be like MK's horizontal up special custom.
At 2:23 I can see a smaller version of this being his dsmash although it would basically be the same as Megaman's soooo...
At 0:05 the gif I showed earlier but I can easily see a sped up version of this being his stage entry.
At 0:10 we get to see him run which could be his running animation if he doesn't glide like MK or could be his fast walking animation.
At 0:14 he blocks which could be his shielding animation. Right after that he does a 3 slash combo like his one from SSU but without the ground beam. Could be a jab or ftilt.
At 0:20 another potential nair. Basically MK's but on steroids and there's a ground beam upon landing.
At 0:41 an upward stab which could be his utilt. Basically the same as MK's though
At 0:50 the closest I can see this move being is a dsmash. Would make it stand out from Megaman's. Would have to be made smaller of course.
At 1:12 a potential Final Smash. Pattern for the blasts would likely have to be random though so players couldn't avoid it super easily.
At 1:21 a potential jab although it's basically MK's in Sm4sh except with a blade beam.
At 1:23 I can actually see that as a potential neutral special. Fires at an upward angle like Bayonetta's Bullet Climax so you wouldn't be able to camp too well with it except against bigger characters. Would be more suited for attacking airborne opponents. Right after he goes into the air and does the same attack angled downwards so it could function like that if done in the air or it could be like Bayonetta's side special and require an extra control stick movement to make it do that. Right after that he does a purely downward one that also shows that the beams reflect off of floors and presumably walls.
At 1:33 another potential Final Smash although it's basically a ripoff of PK Starstorm.
At 2:09 a potential dash attack where he lunges forward with a stab.
At 2:19 literally Brawl Shuttle Loop right there. Could be an up special if they bother to code in gliding again.
At 2:32 he lies on the ground so there's his 'animation' for when that happens in Smash face down anyways.
At 1:03 a potnetial neutral special or up special. It's Mach Tornado but he quickly goes up before going back down which would make it different from MK's which only slowly goes up if you mash b.
At 1:33 another potential Final Smash. I can see it working like Megaman's where if you enter the range of the vortex, you're taken into a cinematic where GK slashes the heck out of you before launching you.
At 2:52 another potnetial neutral or side special. seems to have slight homing properties since the third beam went up as Kirby jumped.
And that's all I could find out of those videos. Spent a longer time than I probably should have looking for a potential moveset for a character that most likely won't ever get in but I need something to keep me awake. And now to catch up on what I missed here!