Vegeta was fully controlled by Babidi?

[Captain Cadaver]

Let's say Vegeta underestimated Babidi's mind control and, for a split second, lowered his guard enough for Babidi to fully control him. With Vegeta proving his loyalty when attempting to kill Shin and Gohan before Goku stops him, how would the arc progress from here? Would Goku be forced to use SS3 to finish things quickly?

 

[Papasmurf]

Vegeta would definitely go for the kill against right away, forcing Galu to fight with him all the sooner. Unfortunately, this means Galu doesn't have a chance to demand Babidi warp them to another location, so they soon end up destroying the Budokai ring. Trying to contain the damage, Galu goes SSJ2 and blasts Vegeta away from the tournament arena, forcing Vegeta to turn SSJ2 as well to block it. Galu probably ends up telling Gohan and Kaioshit to attack Babidi while he has Vegeta occupied with their fight, and because Vegeta is fully possessed at this point, he tries to abandon the fight to give them chase, forcing Galu to turn SSJ3 to defeat him quickly. Afterwards, I guess Galu hones in on Babidi's ki and kills Dabura to reverse Piccolo and Kuririn's petrification before letting Kaioshit deal the final blow to Babidi. Boo isn't released, and Vegeta returns to his normal state, fueled by a new drive to surpass Goku's SSJ3. The events of the BoG arc are altered to Beerus just getting his pudding with Goku remaining dead, and the Earth is destroyed by Freeza months later when he returns to life.

 

[Captain Cadaver]

Considering the time Galu took to go SS3 against Boo, wouldn't him attempting it just provide an opening for Vegeta to attack Gohan and Shin?

 

[Papasmurf]

Considering the time Galu took to go SS3 against Boo, wouldn't him attempting it just provide an opening for Vegeta to attack Gohan and Shin?

It seems to be plot dependent. Galu had no additional experience with going SSJ3 by the time he faced Gotenks-Boo, and he went straight from base to SSJ3 in a moment when it was urgent.

 

[Captain Cadaver]

His display against Gotenks Boo could have been due to the additional instance of using it against Fat Boo making him more used to transforming though, but I guess you could explain it as Galu wanting to stall even further for Trunks, which makes sense.

 

[Papasmurf]

His display against Gotenks Boo could have been due to the additional instance of using it against Fat Boo making him more used to transforming though, but I guess you could explain it as Galu wanting to stall even further for Trunks, which makes sense.

He also spent a little longer powering up to SSJ3 than he did against Gotenks-Boo when he went SSJ3 to fight Kid Boo, as well. It's really not consistent and seems to depend on whatever Toriyama feels like. A similar example would be how Trunks instantly went Grade 2 to give chase to Semi-Perfect Cell, even though it took several pages for Vegeta to do the same.

 

[Captain Cadaver]

To be fair, it could've just been that Vegeta purposely drew out the transformation, considering showing off and proving himself were integral parts of his personality at that point in the series.

 

[Papasmurf]

Gotenks only took a moment to turn SSJ in the manga though, and he was even more of a showboat than Vegeta.

 

[Captain Cadaver]

Gotenks was saving SS3 as his spectacle though, something Trunks made pretty apparent prior to the fusion, so it's understandable why Gotenks didn't bother to drag his SSJ transformation out despite his personality.

 

[Papasmurf]

He was still dragging out attacks like that Boo Boo Volleyball move even after he turned SSJ3 though, so since Piccolo had no idea that he could turn SSJ after fusing it makes sense for him to drag it out.

 

[Captain Cadaver]

Which were techniques he had yet to unveil to an audience yet, unlike SSJ which was old news at that point.

 

[Papasmurf]

Piccolo didn't know he could turn SSJ at will until he saw him do it.

 

[Captain Cadaver]

Whilst that's true, he had already seen SSJ Gotenks in general, making it far from spectacular compared to the other changes Gotenks had to offer.

 

[Papasmurf]

It's still within Gotenks' nature to show off a new ability though.

 

[Boo Brand Milk]

Goku still loses by screwing around. Gohan and Shin probably cheat by going to world of the kais while Vegeta fellates Babidi during Buu's destructive rampage. If anything, he knows exactly where the Z warriors would be hiding. Since all those folks did nothing useful Ultimate Gohan appears and rocks Vegeta. Gohan may kill him, he's different and everyone's dead so he knows using the dragon balls is the only option. Ultimate Gohan/SSJ 3 Goku probably has an easy time with Buu if Majin Vegeta prevents the existence of Gotenks.

 

[Hector]

In canon, Goku withheld SSJ3 before knowing that Vegeta was only half controlled, so he does the same this time too. When Buu is released and Vegeta refuses to let Kakarot go, Goku goes SSJ3 and kills him. Then he goes to find Buu.
Not having enough time left to beat him, he tells him that someone stronger will appear and, after that, things go as in canon.