A possible reason why Gokhan would need SSjin against Bootenks

[Let's Go Fearless!]

Since Ultimate Gohan is a lot stronger than Goku which mean their fusion result would be a disaster and wouldn't be as strong gains like Gotenks received.

 

[Papasmurf]

They'd break down (like Fusion Zamasu) because one of the fusees is full Saiyan and the other has human in him

 

[ekrolo2]

Ignoring Super (because why wouldn't you?) I don't see how Gohan's insanely strong Ultimate state + Goku's wouldn't amount to a fighter capable of destroying Bootenks without SS. Gotenks and Super Boo are weaker than Gohan for sure but not by much, meaning Gohkhan wouldn't need to be more than 2-3 times stronger than Gohan to smash Bootenks.

 

[SSJ2]

Gokhan should get to a level where he can finger flick even Gohan Boo in Base, hell, maybe even SSJ Vegetto depending on where you place him. Goku is still one of the top 3 masters in the world, so there's no way he will have a negative influence on a merge with Gohan.

 

[Let's Go Fearless!]

Gokhan should get to a level where he can finger flick even Gohan Boo in Base, hell, maybe even SSJ Vegetto depending on where you place him. Goku is still one of the top 3 masters in the world, so there's no way he will have a negative influence on a merge with Gohan.

But Gohan is over 1000x stronger than Goku. It would be more like this

 

[Papasmurf]

Gotenks-Boo will perform a fusion dance with his kamikaze ghost to counter Gokhan's massive powa.

 

[sei'taer]

Old kaioshin even tells goku they probably won't need to go SSJ.

 

[Let's Go Fearless!]

Old kaioshin even tells goku they probably won't need to go SSJ.

Metamorian Gokhan.

 

[SSJ2]

Huh? Metamoran Gokhan = Gogeta.