What we know:
- Gokhan would shit stomp Gotenks-Boo without transforming.
- Gokhan could use Super Saiyan despite Ultimate Gohan's ambiguous ability to.
- Vegetto was apparently the "strongest"—"strongest" regarding what exactly, we do not know for sure. Could be of any potential fusions, could be current beings, could be potential fusions of Goku and Vegeta specifically, also eat my ass.
Assuming Vegetto was meant to be superior to Gokhan in all regards, that would put his Base power in another league from even Gohan-Boo, something the anime filler didn't even particularly follow through with. Gokhan would rape Gohan-Boo as well, but may not be too far ahead that he could get past Boo's regeneration on a basic level.
Assuming Vegetto was the strongest of the beings currently around, or between Metamoran and Potara mergers of Goku and Vegeta, that would leave room for Gokhan to be on par with or moderately ahead of Gohan-Boo with Vegetto being anywhere you want so long as his Super Saiyan would still stomp said version of Boo.
I personally like the second interpretation just because it sounds a bit more ridiculous for someone as powerful as Ultimate Gohan to merge with Goku and still be behind a merger of Goku and a relative weakling like Vegeta.
10,000 + 1 = 10,001 * Z becoming 100,000,000 makes more sense than 1 + 1 = 2 * Z becoming 300,000,000.
:nickyoung